Merge changes I878c0b78,Ie4d6469e

* changes:
  Remove recursive glob from server/logging/BUILD
  Split data/ dir from giant server target
diff --git a/java/com/google/gerrit/acceptance/AbstractDaemonTest.java b/java/com/google/gerrit/acceptance/AbstractDaemonTest.java
index 89cc724..10a8852 100644
--- a/java/com/google/gerrit/acceptance/AbstractDaemonTest.java
+++ b/java/com/google/gerrit/acceptance/AbstractDaemonTest.java
@@ -1257,7 +1257,7 @@
 
   protected GroupReference groupRef(AccountGroup.UUID groupUuid) {
     GroupDescription.Basic groupDescription = groupBackend.get(groupUuid);
-    return new GroupReference(groupDescription.getGroupUUID(), groupDescription.getName());
+    return GroupReference.create(groupDescription.getGroupUUID(), groupDescription.getName());
   }
 
   protected InternalGroup group(String groupName) {
@@ -1269,7 +1269,7 @@
   protected GroupReference groupRef(String groupName) {
     InternalGroup group = groupCache.get(AccountGroup.nameKey(groupName)).orElse(null);
     assertThat(group).isNotNull();
-    return new GroupReference(group.getGroupUUID(), group.getName());
+    return GroupReference.create(group.getGroupUUID(), group.getName());
   }
 
   protected AccountGroup.UUID groupUuid(String groupName) {
diff --git a/java/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImpl.java b/java/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImpl.java
index 21bfcd1..de83cff 100644
--- a/java/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImpl.java
+++ b/java/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImpl.java
@@ -154,7 +154,7 @@
         Permission permission =
             projectConfig.getAccessSection(p.section(), true).getPermission(p.name(), true);
         if (p.group().isPresent()) {
-          GroupReference group = new GroupReference(p.group().get(), p.group().get().get());
+          GroupReference group = GroupReference.create(p.group().get(), p.group().get().get());
           group = projectConfig.resolve(group);
           permission.removeRule(group);
         } else {
@@ -325,7 +325,7 @@
   }
 
   private static PermissionRule newRule(ProjectConfig project, AccountGroup.UUID groupUUID) {
-    GroupReference group = new GroupReference(groupUUID, groupUUID.get());
+    GroupReference group = GroupReference.create(groupUUID, groupUUID.get());
     group = project.resolve(group);
     return new PermissionRule(group);
   }
diff --git a/java/com/google/gerrit/common/data/GroupReference.java b/java/com/google/gerrit/common/data/GroupReference.java
index 0af088e..2620138 100644
--- a/java/com/google/gerrit/common/data/GroupReference.java
+++ b/java/com/google/gerrit/common/data/GroupReference.java
@@ -16,16 +16,18 @@
 
 import static java.util.Objects.requireNonNull;
 
+import com.google.auto.value.AutoValue;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.entities.AccountGroup;
 
 /** Describes a group within a projects {@link AccessSection}s. */
-public class GroupReference implements Comparable<GroupReference> {
+@AutoValue
+public abstract class GroupReference implements Comparable<GroupReference> {
 
   private static final String PREFIX = "group ";
 
   public static GroupReference forGroup(GroupDescription.Basic group) {
-    return new GroupReference(group.getGroupUUID(), group.getName());
+    return GroupReference.create(group.getGroupUUID(), group.getName());
   }
 
   public static boolean isGroupReference(String configValue) {
@@ -40,10 +42,10 @@
     return configValue.substring(PREFIX.length()).trim();
   }
 
-  protected String uuid;
-  protected String name;
+  @Nullable
+  public abstract AccountGroup.UUID getUUID();
 
-  protected GroupReference() {}
+  public abstract String getName();
 
   /**
    * Create a group reference.
@@ -51,9 +53,8 @@
    * @param uuid UUID of the group, must not be {@code null}
    * @param name the group name, must not be {@code null}
    */
-  public GroupReference(AccountGroup.UUID uuid, String name) {
-    setUUID(requireNonNull(uuid));
-    setName(name);
+  public static GroupReference create(AccountGroup.UUID uuid, String name) {
+    return new AutoValue_GroupReference(requireNonNull(uuid), requireNonNull(name));
   }
 
   /**
@@ -61,33 +62,12 @@
    *
    * @param name the group name, must not be {@code null}
    */
-  public GroupReference(String name) {
-    setUUID(null);
-    setName(name);
-  }
-
-  @Nullable
-  public AccountGroup.UUID getUUID() {
-    return uuid != null ? AccountGroup.uuid(uuid) : null;
-  }
-
-  public void setUUID(@Nullable AccountGroup.UUID newUUID) {
-    uuid = newUUID != null ? newUUID.get() : null;
-  }
-
-  public String getName() {
-    return name;
-  }
-
-  public void setName(String newName) {
-    if (newName == null) {
-      throw new NullPointerException();
-    }
-    this.name = newName;
+  public static GroupReference create(String name) {
+    return new AutoValue_GroupReference(null, name);
   }
 
   @Override
-  public int compareTo(GroupReference o) {
+  public final int compareTo(GroupReference o) {
     return uuid(this).compareTo(uuid(o));
   }
 
@@ -100,21 +80,21 @@
   }
 
   @Override
-  public int hashCode() {
+  public final int hashCode() {
     return uuid(this).hashCode();
   }
 
   @Override
-  public boolean equals(Object o) {
+  public final boolean equals(Object o) {
     return o instanceof GroupReference && compareTo((GroupReference) o) == 0;
   }
 
-  public String toConfigValue() {
-    return PREFIX + name;
+  @Override
+  public final String toString() {
+    return "Group[" + getName() + " / " + getUUID() + "]";
   }
 
-  @Override
-  public String toString() {
-    return "Group[" + getName() + " / " + getUUID() + "]";
+  public String toConfigValue() {
+    return PREFIX + getName();
   }
 }
diff --git a/java/com/google/gerrit/common/data/PermissionRule.java b/java/com/google/gerrit/common/data/PermissionRule.java
index 8ab0a55..ce94695 100644
--- a/java/com/google/gerrit/common/data/PermissionRule.java
+++ b/java/com/google/gerrit/common/data/PermissionRule.java
@@ -255,8 +255,7 @@
 
     String groupName = GroupReference.extractGroupName(src);
     if (groupName != null) {
-      GroupReference group = new GroupReference();
-      group.setName(groupName);
+      GroupReference group = GroupReference.create(groupName);
       rule.setGroup(group);
     } else {
       throw new IllegalArgumentException("Rule must include group: " + orig);
diff --git a/java/com/google/gerrit/common/data/SubscribeSection.java b/java/com/google/gerrit/common/data/SubscribeSection.java
index 6ac4695..533a2f0 100644
--- a/java/com/google/gerrit/common/data/SubscribeSection.java
+++ b/java/com/google/gerrit/common/data/SubscribeSection.java
@@ -14,43 +14,58 @@
 
 package com.google.gerrit.common.data;
 
+import static com.google.common.collect.ImmutableList.toImmutableList;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.entities.BranchNameKey;
 import com.google.gerrit.entities.Project;
-import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
+import java.util.HashSet;
+import java.util.Set;
+import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.transport.RefSpec;
 
 /** Portion of a {@link Project} describing superproject subscription rules. */
-public class SubscribeSection {
+@AutoValue
+public abstract class SubscribeSection {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
-  private final List<RefSpec> multiMatchRefSpecs;
-  private final List<RefSpec> matchingRefSpecs;
-  private final Project.NameKey project;
+  public abstract Project.NameKey project();
 
-  public SubscribeSection(Project.NameKey p) {
-    project = p;
-    matchingRefSpecs = new ArrayList<>();
-    multiMatchRefSpecs = new ArrayList<>();
+  protected abstract ImmutableList<RefSpec> matchingRefSpecs();
+
+  protected abstract ImmutableList<RefSpec> multiMatchRefSpecs();
+
+  public static Builder builder(Project.NameKey project) {
+    return new AutoValue_SubscribeSection.Builder().project(project);
   }
 
-  public void addMatchingRefSpec(RefSpec spec) {
-    matchingRefSpecs.add(spec);
-  }
+  public abstract Builder toBuilder();
 
-  public void addMatchingRefSpec(String spec) {
-    RefSpec r = new RefSpec(spec);
-    matchingRefSpecs.add(r);
-  }
+  @AutoValue.Builder
+  public abstract static class Builder {
+    public abstract Builder project(Project.NameKey project);
 
-  public void addMultiMatchRefSpec(String spec) {
-    RefSpec r = new RefSpec(spec, RefSpec.WildcardMode.ALLOW_MISMATCH);
-    multiMatchRefSpecs.add(r);
-  }
+    abstract ImmutableList.Builder<RefSpec> matchingRefSpecsBuilder();
 
-  public Project.NameKey getProject() {
-    return project;
+    abstract ImmutableList.Builder<RefSpec> multiMatchRefSpecsBuilder();
+
+    public Builder addMatchingRefSpec(String matchingRefSpec) {
+      matchingRefSpecsBuilder()
+          .add(new RefSpec(matchingRefSpec, RefSpec.WildcardMode.REQUIRE_MATCH));
+      return this;
+    }
+
+    public Builder addMultiMatchRefSpec(String multiMatchRefSpec) {
+      multiMatchRefSpecsBuilder()
+          .add(new RefSpec(multiMatchRefSpec, RefSpec.WildcardMode.ALLOW_MISMATCH));
+      return this;
+    }
+
+    public abstract SubscribeSection build();
   }
 
   /**
@@ -61,12 +76,12 @@
    * @return if the branch could trigger a superproject update
    */
   public boolean appliesTo(BranchNameKey branch) {
-    for (RefSpec r : matchingRefSpecs) {
+    for (RefSpec r : matchingRefSpecs()) {
       if (r.matchSource(branch.branch())) {
         return true;
       }
     }
-    for (RefSpec r : multiMatchRefSpecs) {
+    for (RefSpec r : multiMatchRefSpecs()) {
       if (r.matchSource(branch.branch())) {
         return true;
       }
@@ -74,29 +89,71 @@
     return false;
   }
 
-  public Collection<RefSpec> getMatchingRefSpecs() {
-    return Collections.unmodifiableCollection(matchingRefSpecs);
+  public Collection<String> matchingRefSpecsAsString() {
+    return matchingRefSpecs().stream().map(RefSpec::toString).collect(toImmutableList());
   }
 
-  public Collection<RefSpec> getMultiMatchRefSpecs() {
-    return Collections.unmodifiableCollection(multiMatchRefSpecs);
+  public Collection<String> multiMatchRefSpecsAsString() {
+    return multiMatchRefSpecs().stream().map(RefSpec::toString).collect(toImmutableList());
+  }
+
+  /** Evaluates what the destination branches for the subscription are. */
+  public ImmutableSet<BranchNameKey> getDestinationBranches(
+      BranchNameKey src, Collection<Ref> allRefsInRefsHeads) {
+    Set<BranchNameKey> ret = new HashSet<>();
+    logger.atFine().log("Inspecting SubscribeSection %s", this);
+    for (RefSpec r : matchingRefSpecs()) {
+      logger.atFine().log("Inspecting [matching] ref %s", r);
+      if (!r.matchSource(src.branch())) {
+        continue;
+      }
+      if (r.isWildcard()) {
+        // refs/heads/*[:refs/somewhere/*]
+        ret.add(BranchNameKey.create(project(), r.expandFromSource(src.branch()).getDestination()));
+      } else {
+        // e.g. refs/heads/master[:refs/heads/stable]
+        String dest = r.getDestination();
+        if (dest == null) {
+          dest = r.getSource();
+        }
+        ret.add(BranchNameKey.create(project(), dest));
+      }
+    }
+
+    for (RefSpec r : multiMatchRefSpecs()) {
+      logger.atFine().log("Inspecting [all] ref %s", r);
+      if (!r.matchSource(src.branch())) {
+        continue;
+      }
+      for (Ref ref : allRefsInRefsHeads) {
+        if (r.getDestination() != null && !r.matchDestination(ref.getName())) {
+          continue;
+        }
+        BranchNameKey b = BranchNameKey.create(project(), ref.getName());
+        if (!ret.contains(b)) {
+          ret.add(b);
+        }
+      }
+    }
+    logger.atFine().log("Returning possible branches: %s for project %s", ret, project());
+    return ImmutableSet.copyOf(ret);
   }
 
   @Override
-  public String toString() {
+  public final String toString() {
     StringBuilder ret = new StringBuilder();
     ret.append("[SubscribeSection, project=");
-    ret.append(project);
-    if (!matchingRefSpecs.isEmpty()) {
+    ret.append(project());
+    if (!matchingRefSpecs().isEmpty()) {
       ret.append(", matching=[");
-      for (RefSpec r : matchingRefSpecs) {
+      for (RefSpec r : matchingRefSpecs()) {
         ret.append(r.toString());
         ret.append(", ");
       }
     }
-    if (!multiMatchRefSpecs.isEmpty()) {
+    if (!multiMatchRefSpecs().isEmpty()) {
       ret.append(", all=[");
-      for (RefSpec r : multiMatchRefSpecs) {
+      for (RefSpec r : multiMatchRefSpecs()) {
         ret.append(r.toString());
         ret.append(", ");
       }
diff --git a/java/com/google/gerrit/entities/Project.java b/java/com/google/gerrit/entities/Project.java
index 867b14d..1300b9d 100644
--- a/java/com/google/gerrit/entities/Project.java
+++ b/java/com/google/gerrit/entities/Project.java
@@ -16,6 +16,7 @@
 
 import static java.util.Objects.requireNonNull;
 
+import com.google.errorprone.annotations.Immutable;
 import com.google.gerrit.extensions.client.InheritableBoolean;
 import com.google.gerrit.extensions.client.ProjectState;
 import com.google.gerrit.extensions.client.SubmitType;
@@ -47,7 +48,10 @@
    * <p>Because of this unusual subclassing behavior, this class is not an {@code @AutoValue},
    * unlike other key types in this package. However, this is strictly an implementation detail; its
    * interface and semantics are otherwise analogous to the {@code @AutoValue} types.
+   *
+   * <p>This class is immutable and thread safe.
    */
+  @Immutable
   public static class NameKey implements Serializable, Comparable<NameKey> {
     private static final long serialVersionUID = 1L;
 
@@ -72,25 +76,25 @@
 
     @Override
     public final int hashCode() {
-      return get().hashCode();
+      return name.hashCode();
     }
 
     @Override
     public final boolean equals(Object b) {
       if (b instanceof NameKey) {
-        return get().equals(((NameKey) b).get());
+        return name.equals(((NameKey) b).get());
       }
       return false;
     }
 
     @Override
     public final int compareTo(NameKey o) {
-      return get().compareTo(o.get());
+      return name.compareTo(o.get());
     }
 
     @Override
     public final String toString() {
-      return KeyUtil.encode(get());
+      return KeyUtil.encode(name);
     }
   }
 
diff --git a/java/com/google/gerrit/server/account/ProjectWatches.java b/java/com/google/gerrit/server/account/ProjectWatches.java
index cf63346..6d84f20 100644
--- a/java/com/google/gerrit/server/account/ProjectWatches.java
+++ b/java/com/google/gerrit/server/account/ProjectWatches.java
@@ -219,7 +219,7 @@
       int i = notifyValue.lastIndexOf('[');
       if (i < 0 || notifyValue.charAt(notifyValue.length() - 1) != ']') {
         validationErrorSink.error(
-            new ValidationError(
+            ValidationError.create(
                 WATCH_CONFIG,
                 String.format(
                     "Invalid project watch of account %d for project %s: %s",
@@ -240,7 +240,7 @@
           NotifyType notifyType = Enums.getIfPresent(NotifyType.class, nt).orNull();
           if (notifyType == null) {
             validationErrorSink.error(
-                new ValidationError(
+                ValidationError.create(
                     WATCH_CONFIG,
                     String.format(
                         "Invalid notify type %s in project watch "
diff --git a/java/com/google/gerrit/server/account/StoredPreferences.java b/java/com/google/gerrit/server/account/StoredPreferences.java
index 573c619..79be9e5 100644
--- a/java/com/google/gerrit/server/account/StoredPreferences.java
+++ b/java/com/google/gerrit/server/account/StoredPreferences.java
@@ -183,7 +183,7 @@
       return PreferencesParserUtil.parseGeneralPreferences(cfg, defaultCfg, input);
     } catch (ConfigInvalidException e) {
       validationErrorSink.error(
-          new ValidationError(
+          ValidationError.create(
               PREFERENCES_CONFIG,
               String.format(
                   "Invalid general preferences for account %d: %s",
@@ -197,7 +197,7 @@
       return PreferencesParserUtil.parseDiffPreferences(cfg, defaultCfg, input);
     } catch (ConfigInvalidException e) {
       validationErrorSink.error(
-          new ValidationError(
+          ValidationError.create(
               PREFERENCES_CONFIG,
               String.format(
                   "Invalid diff preferences for account %d: %s", accountId.get(), e.getMessage())));
@@ -210,7 +210,7 @@
       return PreferencesParserUtil.parseEditPreferences(cfg, defaultCfg, input);
     } catch (ConfigInvalidException e) {
       validationErrorSink.error(
-          new ValidationError(
+          ValidationError.create(
               PREFERENCES_CONFIG,
               String.format(
                   "Invalid edit preferences for account %d: %s", accountId.get(), e.getMessage())));
diff --git a/java/com/google/gerrit/server/auth/ldap/LdapGroupBackend.java b/java/com/google/gerrit/server/auth/ldap/LdapGroupBackend.java
index 1d85a5e..e86439a 100644
--- a/java/com/google/gerrit/server/auth/ldap/LdapGroupBackend.java
+++ b/java/com/google/gerrit/server/auth/ldap/LdapGroupBackend.java
@@ -91,7 +91,7 @@
 
   private static GroupReference groupReference(ParameterizedString p, LdapQuery.Result res)
       throws NamingException {
-    return new GroupReference(
+    return GroupReference.create(
         AccountGroup.uuid(LDAP_UUID + res.getDN()), LDAP_NAME + LdapRealm.apply(p, res));
   }
 
diff --git a/java/com/google/gerrit/server/config/AllProjectsName.java b/java/com/google/gerrit/server/config/AllProjectsName.java
index 6d5525c..3a13a58 100644
--- a/java/com/google/gerrit/server/config/AllProjectsName.java
+++ b/java/com/google/gerrit/server/config/AllProjectsName.java
@@ -14,9 +14,15 @@
 
 package com.google.gerrit.server.config;
 
+import com.google.errorprone.annotations.Immutable;
 import com.google.gerrit.entities.Project;
 
-/** Special name of the project that all projects derive from. */
+/**
+ * Special name of the project that all projects derive from.
+ *
+ * <p>This class is immutable and thread safe.
+ */
+@Immutable
 public class AllProjectsName extends Project.NameKey {
   private static final long serialVersionUID = 1L;
 
diff --git a/java/com/google/gerrit/server/config/AllUsersName.java b/java/com/google/gerrit/server/config/AllUsersName.java
index aa92db8..393fb6b 100644
--- a/java/com/google/gerrit/server/config/AllUsersName.java
+++ b/java/com/google/gerrit/server/config/AllUsersName.java
@@ -14,9 +14,15 @@
 
 package com.google.gerrit.server.config;
 
+import com.google.errorprone.annotations.Immutable;
 import com.google.gerrit.entities.Project;
 
-/** Special name of the project in which meta data for all users is stored. */
+/**
+ * Special name of the project in which meta data for all users is stored.
+ *
+ * <p>This class is immutable and thread safe.
+ */
+@Immutable
 public class AllUsersName extends Project.NameKey {
   private static final long serialVersionUID = 1L;
 
diff --git a/java/com/google/gerrit/server/git/BranchOrderSection.java b/java/com/google/gerrit/server/git/BranchOrderSection.java
index 0266655..826067f 100644
--- a/java/com/google/gerrit/server/git/BranchOrderSection.java
+++ b/java/com/google/gerrit/server/git/BranchOrderSection.java
@@ -14,9 +14,12 @@
 
 package com.google.gerrit.server.git;
 
+import static com.google.common.collect.ImmutableList.toImmutableList;
+
+import com.google.auto.value.AutoValue;
 import com.google.common.collect.ImmutableList;
 import com.google.gerrit.entities.RefNames;
-import java.util.List;
+import java.util.Collection;
 
 /**
  * An ordering of branches by stability.
@@ -25,33 +28,36 @@
  * into stable branches. This is configured by the {@code branchOrder.branch} project setting. This
  * class represents the ordered list of branches, by increasing stability.
  */
-public class BranchOrderSection {
+@AutoValue
+public abstract class BranchOrderSection {
 
   /**
    * Branch names ordered from least to the most stable.
    *
    * <p>Typically the order will be like: master, stable-M.N, stable-M.N-1, ...
+   *
+   * <p>Ref names in this list are exactly as they appear in {@code project.config}
    */
-  private final ImmutableList<String> order;
+  public abstract ImmutableList<String> order();
 
-  public BranchOrderSection(String[] order) {
-    if (order.length == 0) {
-      this.order = ImmutableList.of();
-    } else {
-      ImmutableList.Builder<String> builder = ImmutableList.builder();
-      for (String b : order) {
-        builder.add(RefNames.fullName(b));
-      }
-      this.order = builder.build();
-    }
+  public static BranchOrderSection create(Collection<String> order) {
+    // Do not mutate the given list as this will be written back to disk when ProjectConfig is
+    // stored.
+    return new AutoValue_BranchOrderSection(ImmutableList.copyOf(order));
   }
 
-  public String[] getMoreStable(String branch) {
-    int i = order.indexOf(RefNames.fullName(branch));
+  /**
+   * Returns the tail list of branches that are more stable - so lower in the entire list ordered by
+   * priority compared to the provided branch. Always returns a fully qualified ref name (including
+   * the refs/heads/ prefix).
+   */
+  public ImmutableList<String> getMoreStable(String branch) {
+    ImmutableList<String> fullyQualifiedOrder =
+        order().stream().map(RefNames::fullName).collect(toImmutableList());
+    int i = fullyQualifiedOrder.indexOf(RefNames.fullName(branch));
     if (0 <= i) {
-      List<String> r = order.subList(i + 1, order.size());
-      return r.toArray(new String[r.size()]);
+      return fullyQualifiedOrder.subList(i + 1, fullyQualifiedOrder.size());
     }
-    return new String[] {};
+    return ImmutableList.of();
   }
 }
diff --git a/java/com/google/gerrit/server/git/ValidationError.java b/java/com/google/gerrit/server/git/ValidationError.java
index 28d5171..3606c42 100644
--- a/java/com/google/gerrit/server/git/ValidationError.java
+++ b/java/com/google/gerrit/server/git/ValidationError.java
@@ -14,51 +14,26 @@
 
 package com.google.gerrit.server.git;
 
-import java.util.Objects;
+import com.google.auto.value.AutoValue;
 
 /** Indicates a problem with Git based data. */
-public class ValidationError {
-  private final String message;
+@AutoValue
+public abstract class ValidationError {
+  public abstract String getMessage();
 
-  public ValidationError(String file, String message) {
-    this(file + ": " + message);
+  public static ValidationError create(String file, String message) {
+    return create(file + ": " + message);
   }
 
-  public ValidationError(String file, int line, String message) {
-    this(file + ":" + line + ": " + message);
+  public static ValidationError create(String file, int line, String message) {
+    return create(file + ":" + line + ": " + message);
   }
 
-  public ValidationError(String message) {
-    this.message = message;
-  }
-
-  public String getMessage() {
-    return message;
-  }
-
-  @Override
-  public String toString() {
-    return "ValidationError[" + message + "]";
+  public static ValidationError create(String message) {
+    return new AutoValue_ValidationError(message);
   }
 
   public interface Sink {
     void error(ValidationError error);
   }
-
-  @Override
-  public boolean equals(Object o) {
-    if (o == this) {
-      return true;
-    }
-    if (o instanceof ValidationError) {
-      ValidationError that = (ValidationError) o;
-      return Objects.equals(this.message, that.message);
-    }
-    return false;
-  }
-
-  @Override
-  public int hashCode() {
-    return Objects.hashCode(message);
-  }
 }
diff --git a/java/com/google/gerrit/server/git/meta/TabFile.java b/java/com/google/gerrit/server/git/meta/TabFile.java
index c9a8e77..80570a5 100644
--- a/java/com/google/gerrit/server/git/meta/TabFile.java
+++ b/java/com/google/gerrit/server/git/meta/TabFile.java
@@ -59,7 +59,7 @@
 
       int tab = s.indexOf('\t');
       if (tab < 0) {
-        errors.error(new ValidationError(filename, lineNumber, "missing tab delimiter"));
+        errors.error(ValidationError.create(filename, lineNumber, "missing tab delimiter"));
         continue;
       }
 
diff --git a/java/com/google/gerrit/server/group/SystemGroupBackend.java b/java/com/google/gerrit/server/group/SystemGroupBackend.java
index 7821a01..a446718 100644
--- a/java/com/google/gerrit/server/group/SystemGroupBackend.java
+++ b/java/com/google/gerrit/server/group/SystemGroupBackend.java
@@ -104,7 +104,7 @@
       reservedNamesBuilder.add(defaultName);
       String configuredName = cfg.getString("groups", uuid.get(), "name");
       GroupReference ref =
-          new GroupReference(uuid, MoreObjects.firstNonNull(configuredName, defaultName));
+          GroupReference.create(uuid, MoreObjects.firstNonNull(configuredName, defaultName));
       n.put(ref.getName().toLowerCase(Locale.US), ref);
       u.put(ref.getUUID(), ref);
     }
diff --git a/java/com/google/gerrit/server/group/db/GroupNameNotes.java b/java/com/google/gerrit/server/group/db/GroupNameNotes.java
index 70d7a1a..b75670d 100644
--- a/java/com/google/gerrit/server/group/db/GroupNameNotes.java
+++ b/java/com/google/gerrit/server/group/db/GroupNameNotes.java
@@ -443,7 +443,7 @@
       throw new ConfigInvalidException(String.format("UUID for group '%s' must be defined", name));
     }
 
-    return new GroupReference(AccountGroup.uuid(uuid), name);
+    return GroupReference.create(AccountGroup.uuid(uuid), name);
   }
 
   private String getCommitMessage() {
diff --git a/java/com/google/gerrit/server/group/db/RenameGroupOp.java b/java/com/google/gerrit/server/group/db/RenameGroupOp.java
index 420dd33e..4cc6138 100644
--- a/java/com/google/gerrit/server/group/db/RenameGroupOp.java
+++ b/java/com/google/gerrit/server/group/db/RenameGroupOp.java
@@ -125,7 +125,7 @@
         return;
       }
 
-      ref.setName(newName);
+      config.renameGroup(uuid, newName);
       md.getCommitBuilder().setAuthor(author);
       md.setMessage("Rename group " + oldName + " to " + newName + "\n");
       try {
diff --git a/java/com/google/gerrit/server/project/CommentLinkInfoImpl.java b/java/com/google/gerrit/server/project/CommentLinkInfoImpl.java
deleted file mode 100644
index 35de963..0000000
--- a/java/com/google/gerrit/server/project/CommentLinkInfoImpl.java
+++ /dev/null
@@ -1,85 +0,0 @@
-// Copyright (C) 2012 The Android Open Source Project
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package com.google.gerrit.server.project;
-
-import static com.google.common.base.Preconditions.checkArgument;
-
-import com.google.common.base.Strings;
-import com.google.gerrit.extensions.api.projects.CommentLinkInfo;
-
-/** Info about a single commentlink section in a config. */
-public class CommentLinkInfoImpl extends CommentLinkInfo {
-  public static class Enabled extends CommentLinkInfoImpl {
-    public Enabled(String name) {
-      super(name, true);
-    }
-
-    @Override
-    boolean isOverrideOnly() {
-      return true;
-    }
-  }
-
-  public static class Disabled extends CommentLinkInfoImpl {
-    public Disabled(String name) {
-      super(name, false);
-    }
-
-    @Override
-    boolean isOverrideOnly() {
-      return true;
-    }
-  }
-
-  public CommentLinkInfoImpl(String name, String match, String link, String html, Boolean enabled) {
-    checkArgument(name != null, "invalid commentlink.name");
-    checkArgument(!Strings.isNullOrEmpty(match), "invalid commentlink.%s.match", name);
-    link = Strings.emptyToNull(link);
-    html = Strings.emptyToNull(html);
-    checkArgument(
-        (link != null && html == null) || (link == null && html != null),
-        "commentlink.%s must have either link or html",
-        name);
-    this.name = name;
-    this.match = match;
-    this.link = link;
-    this.html = html;
-    this.enabled = enabled;
-  }
-
-  private CommentLinkInfoImpl(CommentLinkInfo src, boolean enabled) {
-    this.name = src.name;
-    this.match = src.match;
-    this.link = src.link;
-    this.html = src.html;
-    this.enabled = enabled;
-  }
-
-  private CommentLinkInfoImpl(String name, boolean enabled) {
-    this.name = name;
-    this.match = null;
-    this.link = null;
-    this.html = null;
-    this.enabled = enabled;
-  }
-
-  boolean isOverrideOnly() {
-    return false;
-  }
-
-  CommentLinkInfo inherit(CommentLinkInfo src) {
-    return new CommentLinkInfoImpl(src, enabled);
-  }
-}
diff --git a/java/com/google/gerrit/server/project/CommentLinkProvider.java b/java/com/google/gerrit/server/project/CommentLinkProvider.java
index 4987d00..500e163 100644
--- a/java/com/google/gerrit/server/project/CommentLinkProvider.java
+++ b/java/com/google/gerrit/server/project/CommentLinkProvider.java
@@ -47,12 +47,12 @@
     List<CommentLinkInfo> cls = Lists.newArrayListWithCapacity(subsections.size());
     for (String name : subsections) {
       try {
-        CommentLinkInfoImpl cl = ProjectConfig.buildCommentLink(cfg, name, true);
-        if (cl.isOverrideOnly()) {
+        StoredCommentLinkInfo cl = ProjectConfig.buildCommentLink(cfg, name, true);
+        if (cl.getOverrideOnly()) {
           logger.atWarning().log("commentlink %s empty except for \"enabled\"", name);
           continue;
         }
-        cls.add(cl);
+        cls.add(cl.toInfo());
       } catch (IllegalArgumentException e) {
         logger.atWarning().log("invalid commentlink: %s", e.getMessage());
       }
diff --git a/java/com/google/gerrit/server/project/ConfiguredMimeTypes.java b/java/com/google/gerrit/server/project/ConfiguredMimeTypes.java
index a6661f7..0447edb 100644
--- a/java/com/google/gerrit/server/project/ConfiguredMimeTypes.java
+++ b/java/com/google/gerrit/server/project/ConfiguredMimeTypes.java
@@ -14,35 +14,38 @@
 
 package com.google.gerrit.server.project;
 
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
 import com.google.common.flogger.FluentLogger;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
 import java.util.Set;
 import java.util.regex.Pattern;
 import java.util.regex.PatternSyntaxException;
+import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.errors.InvalidPatternException;
 import org.eclipse.jgit.fnmatch.FileNameMatcher;
 import org.eclipse.jgit.lib.Config;
 
-public class ConfiguredMimeTypes {
+@AutoValue
+public abstract class ConfiguredMimeTypes {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
   private static final String MIMETYPE = "mimetype";
   private static final String KEY_PATH = "path";
 
-  private final List<TypeMatcher> matchers;
+  protected abstract ImmutableList<TypeMatcher> matchers();
 
-  ConfiguredMimeTypes(String projectName, Config rc) {
+  static ConfiguredMimeTypes create(String projectName, Config rc) {
     Set<String> types = rc.getSubsections(MIMETYPE);
-    if (types.isEmpty()) {
-      matchers = Collections.emptyList();
-    } else {
-      matchers = new ArrayList<>();
+    ImmutableList.Builder<TypeMatcher> matchers = ImmutableList.builder();
+    if (!types.isEmpty()) {
       for (String typeName : types) {
         for (String path : rc.getStringList(MIMETYPE, typeName, KEY_PATH)) {
           try {
-            add(typeName, path);
+            if (path.startsWith("^")) {
+              matchers.add(new ReType(typeName, path));
+            } else {
+              matchers.add(new FnType(typeName, path));
+            }
           } catch (PatternSyntaxException | InvalidPatternException e) {
             logger.atWarning().log(
                 "Ignoring invalid %s.%s.%s = %s in project %s: %s",
@@ -51,19 +54,12 @@
         }
       }
     }
+    return new AutoValue_ConfiguredMimeTypes(matchers.build());
   }
 
-  private void add(String typeName, String path)
-      throws PatternSyntaxException, InvalidPatternException {
-    if (path.startsWith("^")) {
-      matchers.add(new ReType(typeName, path));
-    } else {
-      matchers.add(new FnType(typeName, path));
-    }
-  }
-
+  @Nullable
   public String getMimeType(String path) {
-    for (TypeMatcher m : matchers) {
+    for (TypeMatcher m : matchers()) {
       if (m.matches(path)) {
         return m.type;
       }
@@ -71,42 +67,42 @@
     return null;
   }
 
-  private abstract static class TypeMatcher {
-    final String type;
+  protected abstract static class TypeMatcher {
+    private final String type;
 
-    TypeMatcher(String type) {
+    private TypeMatcher(String type) {
       this.type = type;
     }
 
-    abstract boolean matches(String path);
+    protected abstract boolean matches(String path);
   }
 
-  private static class FnType extends TypeMatcher {
+  protected static class FnType extends TypeMatcher {
     private final FileNameMatcher matcher;
 
-    FnType(String type, String pattern) throws InvalidPatternException {
+    private FnType(String type, String pattern) throws InvalidPatternException {
       super(type);
       this.matcher = new FileNameMatcher(pattern, null);
     }
 
     @Override
-    boolean matches(String input) {
+    protected boolean matches(String input) {
       FileNameMatcher m = new FileNameMatcher(matcher);
       m.append(input);
       return m.isMatch();
     }
   }
 
-  private static class ReType extends TypeMatcher {
+  protected static class ReType extends TypeMatcher {
     private final Pattern re;
 
-    ReType(String type, String pattern) throws PatternSyntaxException {
+    private ReType(String type, String pattern) throws PatternSyntaxException {
       super(type);
       this.re = Pattern.compile(pattern);
     }
 
     @Override
-    boolean matches(String input) {
+    protected boolean matches(String input) {
       return re.matcher(input).matches();
     }
   }
diff --git a/java/com/google/gerrit/server/project/GroupList.java b/java/com/google/gerrit/server/project/GroupList.java
index ba7dc95..7237bb6 100644
--- a/java/com/google/gerrit/server/project/GroupList.java
+++ b/java/com/google/gerrit/server/project/GroupList.java
@@ -15,6 +15,7 @@
 package com.google.gerrit.server.project;
 
 import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.common.data.GroupReference;
 import com.google.gerrit.entities.AccountGroup;
 import com.google.gerrit.entities.Project;
@@ -56,7 +57,7 @@
       }
       AccountGroup.UUID uuid = AccountGroup.uuid(row.left);
       String name = row.right;
-      GroupReference ref = new GroupReference(uuid, name);
+      GroupReference ref = GroupReference.create(uuid, name);
 
       groupsByUUID.put(uuid, ref);
     }
@@ -64,10 +65,26 @@
     return new GroupList(groupsByUUID);
   }
 
+  @Nullable
   public GroupReference byUUID(AccountGroup.UUID uuid) {
     return byUUID.get(uuid);
   }
 
+  @Nullable
+  public GroupReference byName(String name) {
+    return byUUID.entrySet().stream()
+        .map(Map.Entry::getValue)
+        .filter(groupReference -> name.equals(groupReference.getName()))
+        .findAny()
+        .orElse(null);
+  }
+
+  /**
+   * Returns the {@link GroupReference} instance that {@link GroupList} holds on to that has the
+   * same {@link com.google.gerrit.entities.AccountGroup.UUID} as the argument. Will store the
+   * argument internally, if no group with this {@link com.google.gerrit.entities.AccountGroup.UUID}
+   * was stored previously.
+   */
   public GroupReference resolve(GroupReference group) {
     if (group != null) {
       if (group.getUUID() == null || group.getUUID().get() == null) {
@@ -86,6 +103,10 @@
     return group;
   }
 
+  public void renameGroup(AccountGroup.UUID uuid, String name) {
+    byUUID.replace(uuid, GroupReference.create(uuid, name));
+  }
+
   public Collection<GroupReference> references() {
     return byUUID.values();
   }
diff --git a/java/com/google/gerrit/server/project/ProjectConfig.java b/java/com/google/gerrit/server/project/ProjectConfig.java
index 4ab583d..2d4928a 100644
--- a/java/com/google/gerrit/server/project/ProjectConfig.java
+++ b/java/com/google/gerrit/server/project/ProjectConfig.java
@@ -91,7 +91,6 @@
 import org.eclipse.jgit.lib.StoredConfig;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.storage.file.FileBasedConfig;
-import org.eclipse.jgit.transport.RefSpec;
 import org.eclipse.jgit.util.FS;
 
 public class ProjectConfig extends VersionedMetaData implements ValidationError.Sink {
@@ -241,7 +240,7 @@
   private Map<String, LabelType> labelSections;
   private ConfiguredMimeTypes mimeTypes;
   private Map<Project.NameKey, SubscribeSection> subscribeSections;
-  private Map<String, CommentLinkInfoImpl> commentLinkSections;
+  private Map<String, StoredCommentLinkInfo> commentLinkSections;
   private List<ValidationError> validationErrors;
   private ObjectId rulesId;
   private long maxObjectSizeLimit;
@@ -250,9 +249,8 @@
   private Set<String> sectionsWithUnknownPermissions;
   private boolean hasLegacyPermissions;
   private Map<String, List<String>> extensionPanelSections;
-  private Map<String, GroupReference> groupsByName;
 
-  public static CommentLinkInfoImpl buildCommentLink(Config cfg, String name, boolean allowRaw)
+  public static StoredCommentLinkInfo buildCommentLink(Config cfg, String name, boolean allowRaw)
       throws IllegalArgumentException {
     String match = cfg.getString(COMMENTLINK, name, KEY_MATCH);
     if (match != null) {
@@ -282,15 +280,21 @@
         && !hasHtml
         && enabled != null) {
       if (enabled) {
-        return new CommentLinkInfoImpl.Enabled(name);
+        return StoredCommentLinkInfo.enabled(name);
       }
-      return new CommentLinkInfoImpl.Disabled(name);
+      return StoredCommentLinkInfo.disabled(name);
     }
-    return new CommentLinkInfoImpl(name, match, link, html, enabled);
+    return StoredCommentLinkInfo.builder(name)
+        .setMatch(match)
+        .setLink(link)
+        .setHtml(html)
+        .setEnabled(enabled)
+        .setOverrideOnly(false)
+        .build();
   }
 
-  public void addCommentLinkSection(CommentLinkInfoImpl commentLink) {
-    commentLinkSections.put(commentLink.name, commentLink);
+  public void addCommentLinkSection(StoredCommentLinkInfo commentLink) {
+    commentLinkSections.put(commentLink.getName(), commentLink);
   }
 
   public void removeCommentLinkSection(String name) {
@@ -358,6 +362,10 @@
     return branchOrderSection;
   }
 
+  public void setBranchOrderSection(BranchOrderSection branchOrderSection) {
+    this.branchOrderSection = branchOrderSection;
+  }
+
   public Map<Project.NameKey, SubscribeSection> getSubscribeSections() {
     return subscribeSections;
   }
@@ -373,7 +381,7 @@
   }
 
   public void addSubscribeSection(SubscribeSection s) {
-    subscribeSections.put(s.getProject(), s);
+    subscribeSections.put(s.project(), s);
   }
 
   public void remove(AccessSection section) {
@@ -476,7 +484,7 @@
     return labelSections;
   }
 
-  public Collection<CommentLinkInfoImpl> getCommentLinkSections() {
+  public Collection<StoredCommentLinkInfo> getCommentLinkSections() {
     return commentLinkSections.values();
   }
 
@@ -485,13 +493,11 @@
   }
 
   public GroupReference resolve(GroupReference group) {
-    GroupReference groupRef = groupList.resolve(group);
-    if (groupRef != null
-        && groupRef.getUUID() != null
-        && !groupsByName.containsKey(groupRef.getName())) {
-      groupsByName.put(groupRef.getName(), groupRef);
-    }
-    return groupRef;
+    return groupList.resolve(group);
+  }
+
+  public void renameGroup(AccountGroup.UUID uuid, String newName) {
+    groupList.renameGroup(uuid, newName);
   }
 
   /** @return the group reference, if the group is used by at least one rule. */
@@ -504,7 +510,7 @@
    *     at least one rule or plugin value.
    */
   public GroupReference getGroup(String groupName) {
-    return groupsByName.get(groupName);
+    return groupList.byName(groupName);
   }
 
   /** @return set of all groups used by this configuration. */
@@ -541,7 +547,7 @@
       GroupDescription.Basic g = groupBackend.get(ref.getUUID());
       if (g != null && !g.getName().equals(ref.getName())) {
         dirty = true;
-        ref.setName(g.getName());
+        groupList.renameGroup(ref.getUUID(), g.getName());
       }
     }
     return dirty;
@@ -570,7 +576,6 @@
       baseConfig.load();
     }
     readGroupList();
-    groupsByName = mapGroupReferences();
 
     rulesId = getObjectId("rules.pl");
     Config rc = readConfig(PROJECT_CONFIG, baseConfig);
@@ -588,7 +593,7 @@
     if (rc.getStringList(ACCESS, null, KEY_INHERIT_FROM).length > 1) {
       // The config must not contain more than one parent to inherit from
       // as there is no guarantee which of the parents would be used then.
-      error(new ValidationError(PROJECT_CONFIG, "Cannot inherit from multiple projects"));
+      error(ValidationError.create(PROJECT_CONFIG, "Cannot inherit from multiple projects"));
     }
     p.setParentName(rc.getString(ACCESS, null, KEY_INHERIT_FROM));
 
@@ -619,7 +624,7 @@
     loadLabelSections(rc);
     loadCommentLinkSections(rc);
     loadSubscribeSections(rc);
-    mimeTypes = new ConfiguredMimeTypes(projectName.get(), rc);
+    mimeTypes = ConfiguredMimeTypes.create(projectName.get(), rc);
     loadPluginSections(rc);
     loadReceiveSection(rc);
     loadExtensionPanelSections(rc);
@@ -628,7 +633,7 @@
   private void loadAccountsSection(Config rc) {
     accountsSection = new AccountsSection();
     accountsSection.setSameGroupVisibility(
-        loadPermissionRules(rc, ACCOUNTS, null, KEY_SAME_GROUP_VISIBILITY, groupsByName, false));
+        loadPermissionRules(rc, ACCOUNTS, null, KEY_SAME_GROUP_VISIBILITY, false));
   }
 
   private void loadExtensionPanelSections(Config rc) {
@@ -638,7 +643,7 @@
       String lower = name.toLowerCase();
       if (lowerNames.containsKey(lower)) {
         error(
-            new ValidationError(
+            ValidationError.create(
                 PROJECT_CONFIG,
                 String.format(
                     "Extension Panels \"%s\" conflicts with \"%s\"", name, lowerNames.get(lower))));
@@ -656,20 +661,18 @@
       ContributorAgreement ca = getContributorAgreement(name, true);
       ca.setDescription(rc.getString(CONTRIBUTOR_AGREEMENT, name, KEY_DESCRIPTION));
       ca.setAgreementUrl(rc.getString(CONTRIBUTOR_AGREEMENT, name, KEY_AGREEMENT_URL));
-      ca.setAccepted(
-          loadPermissionRules(rc, CONTRIBUTOR_AGREEMENT, name, KEY_ACCEPTED, groupsByName, false));
+      ca.setAccepted(loadPermissionRules(rc, CONTRIBUTOR_AGREEMENT, name, KEY_ACCEPTED, false));
       ca.setExcludeProjectsRegexes(
           loadPatterns(rc, CONTRIBUTOR_AGREEMENT, name, KEY_EXCLUDE_PROJECTS));
       ca.setMatchProjectsRegexes(loadPatterns(rc, CONTRIBUTOR_AGREEMENT, name, KEY_MATCH_PROJECTS));
 
       List<PermissionRule> rules =
-          loadPermissionRules(
-              rc, CONTRIBUTOR_AGREEMENT, name, KEY_AUTO_VERIFY, groupsByName, false);
+          loadPermissionRules(rc, CONTRIBUTOR_AGREEMENT, name, KEY_AUTO_VERIFY, false);
       if (rules.isEmpty()) {
         ca.setAutoVerify(null);
       } else if (rules.size() > 1) {
         error(
-            new ValidationError(
+            ValidationError.create(
                 PROJECT_CONFIG,
                 "Invalid rule in "
                     + CONTRIBUTOR_AGREEMENT
@@ -680,7 +683,7 @@
                     + ": at most one group may be set"));
       } else if (rules.get(0).getAction() != Action.ALLOW) {
         error(
-            new ValidationError(
+            ValidationError.create(
                 PROJECT_CONFIG,
                 "Invalid rule in "
                     + CONTRIBUTOR_AGREEMENT
@@ -728,27 +731,26 @@
       for (String dst : rc.getStringList(NOTIFY, sectionName, KEY_EMAIL)) {
         String groupName = GroupReference.extractGroupName(dst);
         if (groupName != null) {
-          GroupReference ref = groupsByName.get(groupName);
+          GroupReference ref = groupList.byName(groupName);
           if (ref == null) {
-            ref = new GroupReference(groupName);
-            groupsByName.put(ref.getName(), ref);
+            ref = groupList.resolve(GroupReference.create(groupName));
           }
           if (ref.getUUID() != null) {
             n.addEmail(ref);
           } else {
             error(
-                new ValidationError(
+                ValidationError.create(
                     PROJECT_CONFIG,
                     "group \"" + ref.getName() + "\" not in " + GroupList.FILE_NAME));
           }
         } else if (dst.startsWith("user ")) {
-          error(new ValidationError(PROJECT_CONFIG, dst + " not supported"));
+          error(ValidationError.create(PROJECT_CONFIG, dst + " not supported"));
         } else {
           try {
             n.addEmail(Address.parse(dst));
           } catch (IllegalArgumentException err) {
             error(
-                new ValidationError(
+                ValidationError.create(
                     PROJECT_CONFIG,
                     "notify section \"" + sectionName + "\" has invalid email \"" + dst + "\""));
           }
@@ -779,13 +781,7 @@
           if (isCoreOrPluginPermission(convertedName)) {
             Permission perm = as.getPermission(convertedName, true);
             loadPermissionRules(
-                rc,
-                ACCESS,
-                refName,
-                varName,
-                groupsByName,
-                perm,
-                Permission.hasRange(convertedName));
+                rc, ACCESS, refName, varName, perm, Permission.hasRange(convertedName));
           } else {
             sectionsWithUnknownPermissions.add(as.getName());
           }
@@ -800,8 +796,7 @@
         accessSections.put(AccessSection.GLOBAL_CAPABILITIES, capability);
       }
       Permission perm = capability.getPermission(varName, true);
-      loadPermissionRules(
-          rc, CAPABILITY, null, varName, groupsByName, perm, GlobalCapability.hasRange(varName));
+      loadPermissionRules(rc, CAPABILITY, null, varName, perm, GlobalCapability.hasRange(varName));
     }
   }
 
@@ -815,7 +810,7 @@
     try {
       RefPattern.validateRegExp(refPattern);
     } catch (InvalidNameException e) {
-      error(new ValidationError(PROJECT_CONFIG, "Invalid ref name: " + e.getMessage()));
+      error(ValidationError.create(PROJECT_CONFIG, "Invalid ref name: " + e.getMessage()));
       return false;
     }
     return true;
@@ -823,7 +818,14 @@
 
   private void loadBranchOrderSection(Config rc) {
     if (rc.getSections().contains(BRANCH_ORDER)) {
-      branchOrderSection = new BranchOrderSection(rc.getStringList(BRANCH_ORDER, null, BRANCH));
+      branchOrderSection =
+          BranchOrderSection.create(Arrays.asList(rc.getStringList(BRANCH_ORDER, null, BRANCH)));
+    }
+  }
+
+  private void saveBranchOrderSection(Config rc) {
+    if (branchOrderSection != null) {
+      rc.setStringList(BRANCH_ORDER, null, BRANCH, branchOrderSection.order());
     }
   }
 
@@ -836,7 +838,9 @@
         // to fail fast if any of the patterns are invalid.
         patterns.add(Pattern.compile(patternString).pattern());
       } catch (PatternSyntaxException e) {
-        error(new ValidationError(PROJECT_CONFIG, "Invalid regular expression: " + e.getMessage()));
+        error(
+            ValidationError.create(
+                PROJECT_CONFIG, "Invalid regular expression: " + e.getMessage()));
         continue;
       }
     }
@@ -844,14 +848,9 @@
   }
 
   private ImmutableList<PermissionRule> loadPermissionRules(
-      Config rc,
-      String section,
-      String subsection,
-      String varName,
-      Map<String, GroupReference> groupsByName,
-      boolean useRange) {
+      Config rc, String section, String subsection, String varName, boolean useRange) {
     Permission perm = new Permission(varName);
-    loadPermissionRules(rc, section, subsection, varName, groupsByName, perm, useRange);
+    loadPermissionRules(rc, section, subsection, varName, perm, useRange);
     return ImmutableList.copyOf(perm.getRules());
   }
 
@@ -860,7 +859,6 @@
       String section,
       String subsection,
       String varName,
-      Map<String, GroupReference> groupsByName,
       Permission perm,
       boolean useRange) {
     for (String ruleString : rc.getStringList(section, subsection, varName)) {
@@ -869,7 +867,7 @@
         rule = PermissionRule.fromString(ruleString, useRange);
       } catch (IllegalArgumentException notRule) {
         error(
-            new ValidationError(
+            ValidationError.create(
                 PROJECT_CONFIG,
                 "Invalid rule in "
                     + section
@@ -881,16 +879,15 @@
         continue;
       }
 
-      GroupReference ref = groupsByName.get(rule.getGroup().getName());
+      GroupReference ref = groupList.byName(rule.getGroup().getName());
       if (ref == null) {
         // The group wasn't mentioned in the groups table, so there is
         // no valid UUID for it. Pool the reference anyway so at least
         // all rules in the same file share the same GroupReference.
         //
-        ref = rule.getGroup();
-        groupsByName.put(ref.getName(), ref);
+        ref = groupList.resolve(rule.getGroup());
         error(
-            new ValidationError(
+            ValidationError.create(
                 PROJECT_CONFIG, "group \"" + ref.getName() + "\" not in " + GroupList.FILE_NAME));
       }
 
@@ -917,7 +914,7 @@
       String lower = name.toLowerCase();
       if (lowerNames.containsKey(lower)) {
         error(
-            new ValidationError(
+            ValidationError.create(
                 PROJECT_CONFIG,
                 String.format("Label \"%s\" conflicts with \"%s\"", name, lowerNames.get(lower))));
       }
@@ -932,13 +929,13 @@
             values.add(labelValue);
           } else {
             error(
-                new ValidationError(
+                ValidationError.create(
                     PROJECT_CONFIG,
                     String.format("Duplicate %s \"%s\" for label \"%s\"", KEY_VALUE, value, name)));
           }
         } catch (IllegalArgumentException notValue) {
           error(
-              new ValidationError(
+              ValidationError.create(
                   PROJECT_CONFIG,
                   String.format(
                       "Invalid %s \"%s\" for label \"%s\": %s",
@@ -950,7 +947,7 @@
       try {
         label = new LabelType(name, values);
       } catch (IllegalArgumentException badName) {
-        error(new ValidationError(PROJECT_CONFIG, String.format("Invalid label \"%s\"", name)));
+        error(ValidationError.create(PROJECT_CONFIG, String.format("Invalid label \"%s\"", name)));
         continue;
       }
 
@@ -961,7 +958,7 @@
               : Optional.of(LabelFunction.MAX_WITH_BLOCK);
       if (!function.isPresent()) {
         error(
-            new ValidationError(
+            ValidationError.create(
                 PROJECT_CONFIG,
                 String.format(
                     "Invalid %s for label \"%s\". Valid names are: %s",
@@ -975,7 +972,7 @@
           label.setDefaultValue(dv);
         } else {
           error(
-              new ValidationError(
+              ValidationError.create(
                   PROJECT_CONFIG,
                   String.format(
                       "Invalid %s \"%s\" for label \"%s\"", KEY_DEFAULT_VALUE, dv, name)));
@@ -1021,14 +1018,14 @@
           short copyValue = Shorts.checkedCast(PermissionRule.parseInt(value));
           if (!copyValues.add(copyValue)) {
             error(
-                new ValidationError(
+                ValidationError.create(
                     PROJECT_CONFIG,
                     String.format(
                         "Duplicate %s \"%s\" for label \"%s\"", KEY_COPY_VALUE, value, name)));
           }
         } catch (IllegalArgumentException notValue) {
           error(
-              new ValidationError(
+              ValidationError.create(
                   PROJECT_CONFIG,
                   String.format(
                       "Invalid %s \"%s\" for label \"%s\": %s",
@@ -1066,14 +1063,14 @@
         commentLinkSections.put(name, buildCommentLink(rc, name, false));
       } catch (PatternSyntaxException e) {
         error(
-            new ValidationError(
+            ValidationError.create(
                 PROJECT_CONFIG,
                 String.format(
                     "Invalid pattern \"%s\" in commentlink.%s.match: %s",
                     rc.getString(COMMENTLINK, name, KEY_MATCH), name, e.getMessage())));
       } catch (IllegalArgumentException e) {
         error(
-            new ValidationError(
+            ValidationError.create(
                 PROJECT_CONFIG,
                 String.format(
                     "Error in pattern \"%s\" in commentlink.%s.match: %s",
@@ -1088,7 +1085,7 @@
     try {
       for (String projectName : subsections) {
         Project.NameKey p = Project.nameKey(projectName);
-        SubscribeSection ss = new SubscribeSection(p);
+        SubscribeSection.Builder ss = SubscribeSection.builder(p);
         for (String s :
             rc.getStringList(SUBSCRIBE_SECTION, projectName, SUBSCRIBE_MULTI_MATCH_REFS)) {
           ss.addMultiMatchRefSpec(s);
@@ -1096,7 +1093,7 @@
         for (String s : rc.getStringList(SUBSCRIBE_SECTION, projectName, SUBSCRIBE_MATCH_REFS)) {
           ss.addMatchingRefSpec(s);
         }
-        subscribeSections.put(p, ss);
+        subscribeSections.put(p, ss.build());
       }
     } catch (IllegalArgumentException e) {
       throw new ConfigInvalidException(e.getMessage());
@@ -1117,10 +1114,10 @@
         String value = rc.getString(PLUGIN, plugin, name);
         String groupName = GroupReference.extractGroupName(value);
         if (groupName != null) {
-          GroupReference ref = groupsByName.get(groupName);
+          GroupReference ref = groupList.byName(groupName);
           if (ref == null) {
             error(
-                new ValidationError(
+                ValidationError.create(
                     PROJECT_CONFIG, "group \"" + groupName + "\" not in " + GroupList.FILE_NAME));
           }
           rc.setString(PLUGIN, plugin, name, value);
@@ -1144,16 +1141,6 @@
     groupList = GroupList.parse(projectName, readUTF8(GroupList.FILE_NAME), this);
   }
 
-  private Map<String, GroupReference> mapGroupReferences() {
-    Collection<GroupReference> references = groupList.references();
-    Map<String, GroupReference> result = new HashMap<>(references.size());
-    for (GroupReference ref : references) {
-      result.put(ref.getName(), ref);
-    }
-
-    return result;
-  }
-
   @Override
   protected boolean onSave(CommitBuilder commit) throws IOException, ConfigInvalidException {
     if (commit.getMessage() == null || "".equals(commit.getMessage())) {
@@ -1204,6 +1191,7 @@
     saveLabelSections(rc);
     saveCommentLinkSections(rc);
     saveSubscribeSections(rc);
+    saveBranchOrderSection(rc);
 
     saveConfig(PROJECT_CONFIG, rc);
     saveGroupList();
@@ -1252,16 +1240,16 @@
   private void saveCommentLinkSections(Config rc) {
     unsetSection(rc, COMMENTLINK);
     if (commentLinkSections != null) {
-      for (CommentLinkInfoImpl cm : commentLinkSections.values()) {
-        rc.setString(COMMENTLINK, cm.name, KEY_MATCH, cm.match);
-        if (!Strings.isNullOrEmpty(cm.html)) {
-          rc.setString(COMMENTLINK, cm.name, KEY_HTML, cm.html);
+      for (StoredCommentLinkInfo cm : commentLinkSections.values()) {
+        rc.setString(COMMENTLINK, cm.getName(), KEY_MATCH, cm.getMatch());
+        if (!Strings.isNullOrEmpty(cm.getHtml())) {
+          rc.setString(COMMENTLINK, cm.getName(), KEY_HTML, cm.getHtml());
         }
-        if (!Strings.isNullOrEmpty(cm.link)) {
-          rc.setString(COMMENTLINK, cm.name, KEY_LINK, cm.link);
+        if (!Strings.isNullOrEmpty(cm.getLink())) {
+          rc.setString(COMMENTLINK, cm.getName(), KEY_LINK, cm.getLink());
         }
-        if (cm.enabled != null && !cm.enabled) {
-          rc.setBoolean(COMMENTLINK, cm.name, KEY_ENABLED, cm.enabled);
+        if (cm.getEnabled() != null && !cm.getEnabled()) {
+          rc.setBoolean(COMMENTLINK, cm.getName(), KEY_ENABLED, cm.getEnabled());
         }
       }
     }
@@ -1558,7 +1546,7 @@
         String value = pluginConfig.getString(PLUGIN, plugin, name);
         String groupName = GroupReference.extractGroupName(value);
         if (groupName != null) {
-          GroupReference ref = groupsByName.get(groupName);
+          GroupReference ref = groupList.byName(groupName);
           if (ref != null && ref.getUUID() != null) {
             keepGroups.add(ref.getUUID());
             pluginConfig.setString(PLUGIN, plugin, name, "group " + ref.getName());
@@ -1578,14 +1566,14 @@
     for (Project.NameKey p : subscribeSections.keySet()) {
       SubscribeSection s = subscribeSections.get(p);
       List<String> matchings = new ArrayList<>();
-      for (RefSpec r : s.getMatchingRefSpecs()) {
-        matchings.add(r.toString());
+      for (String r : s.matchingRefSpecsAsString()) {
+        matchings.add(r);
       }
       rc.setStringList(SUBSCRIBE_SECTION, p.get(), SUBSCRIBE_MATCH_REFS, matchings);
 
       List<String> multimatchs = new ArrayList<>();
-      for (RefSpec r : s.getMultiMatchRefSpecs()) {
-        multimatchs.add(r.toString());
+      for (String r : s.multiMatchRefSpecsAsString()) {
+        multimatchs.add(r);
       }
       rc.setStringList(SUBSCRIBE_SECTION, p.get(), SUBSCRIBE_MULTI_MATCH_REFS, multimatchs);
     }
@@ -1603,7 +1591,7 @@
     try {
       return rc.getEnum(section, subsection, name, defaultValue);
     } catch (IllegalArgumentException err) {
-      error(new ValidationError(PROJECT_CONFIG, err.getMessage()));
+      error(ValidationError.create(PROJECT_CONFIG, err.getMessage()));
       return defaultValue;
     }
   }
diff --git a/java/com/google/gerrit/server/project/ProjectState.java b/java/com/google/gerrit/server/project/ProjectState.java
index efadcc8..1c7c7d6 100644
--- a/java/com/google/gerrit/server/project/ProjectState.java
+++ b/java/com/google/gerrit/server/project/ProjectState.java
@@ -457,16 +457,16 @@
       cls.put(cl.name.toLowerCase(), cl);
     }
     for (ProjectState s : treeInOrder()) {
-      for (CommentLinkInfoImpl cl : s.getConfig().getCommentLinkSections()) {
-        String name = cl.name.toLowerCase();
-        if (cl.isOverrideOnly()) {
+      for (StoredCommentLinkInfo cl : s.getConfig().getCommentLinkSections()) {
+        String name = cl.getName().toLowerCase();
+        if (cl.getOverrideOnly()) {
           CommentLinkInfo parent = cls.get(name);
           if (parent == null) {
             continue; // Ignore invalid overrides.
           }
-          cls.put(name, cl.inherit(parent));
+          cls.put(name, StoredCommentLinkInfo.fromInfo(parent, cl.getEnabled()).toInfo());
         } else {
-          cls.put(name, cl);
+          cls.put(name, cl.toInfo());
         }
       }
     }
diff --git a/java/com/google/gerrit/server/project/StoredCommentLinkInfo.java b/java/com/google/gerrit/server/project/StoredCommentLinkInfo.java
new file mode 100644
index 0000000..4e311b8
--- /dev/null
+++ b/java/com/google/gerrit/server/project/StoredCommentLinkInfo.java
@@ -0,0 +1,133 @@
+// Copyright (C) 2012 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.project;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Strings;
+import com.google.gerrit.common.Nullable;
+import com.google.gerrit.extensions.api.projects.CommentLinkInfo;
+
+/** Info about a single commentlink section in a config. */
+@AutoValue
+public abstract class StoredCommentLinkInfo {
+  public abstract String getName();
+
+  /** A regular expression to match for the commentlink to apply. */
+  @Nullable
+  public abstract String getMatch();
+
+  /** The link to replace the match with. This can only be set if html is {@code null}. */
+  @Nullable
+  public abstract String getLink();
+
+  /** The html to replace the match with. This can only be set if link is {@code null}. */
+  @Nullable
+  public abstract String getHtml();
+
+  /** Weather this comment link is active. {@code null} means true. */
+  @Nullable
+  public abstract Boolean getEnabled();
+
+  /** If set, {@link StoredCommentLinkInfo} has to be overriden to take any effect. */
+  public abstract boolean getOverrideOnly();
+
+  /**
+   * Creates an enabled {@link StoredCommentLinkInfo} that can be overriden but doesn't do anything
+   * on its own.
+   */
+  public static StoredCommentLinkInfo enabled(String name) {
+    return builder(name).setOverrideOnly(true).build();
+  }
+
+  /**
+   * Creates a disabled {@link StoredCommentLinkInfo} that can be overriden but doesn't do anything
+   * on it's own.
+   */
+  public static StoredCommentLinkInfo disabled(String name) {
+    return builder(name).setOverrideOnly(true).build();
+  }
+
+  /** Creates and returns a new {@link StoredCommentLinkInfo.Builder} instance. */
+  public static Builder builder(String name) {
+    checkArgument(name != null, "invalid commentlink.name");
+    return new AutoValue_StoredCommentLinkInfo.Builder().setName(name).setOverrideOnly(false);
+  }
+
+  /** Creates and returns a new {@link StoredCommentLinkInfo} instance with the same values. */
+  static StoredCommentLinkInfo fromInfo(CommentLinkInfo src, boolean enabled) {
+    return builder(src.name)
+        .setMatch(src.match)
+        .setLink(src.link)
+        .setHtml(src.html)
+        .setEnabled(enabled)
+        .setOverrideOnly(false)
+        .build();
+  }
+
+  /** Returns an {@link CommentLinkInfo} instance with the same values. */
+  CommentLinkInfo toInfo() {
+    CommentLinkInfo info = new CommentLinkInfo();
+    info.name = getName();
+    info.match = getMatch();
+    info.link = getLink();
+    info.html = getHtml();
+    info.enabled = getEnabled();
+    return info;
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder {
+    public abstract Builder setName(String value);
+
+    public abstract Builder setMatch(@Nullable String value);
+
+    public abstract Builder setLink(@Nullable String value);
+
+    public abstract Builder setHtml(@Nullable String value);
+
+    public abstract Builder setEnabled(@Nullable Boolean value);
+
+    public abstract Builder setOverrideOnly(boolean value);
+
+    public StoredCommentLinkInfo build() {
+      checkArgument(getName() != null, "invalid commentlink.name");
+      setLink(Strings.emptyToNull(getLink()));
+      setHtml(Strings.emptyToNull(getHtml()));
+      if (!getOverrideOnly()) {
+        checkArgument(
+            !Strings.isNullOrEmpty(getMatch()), "invalid commentlink.%s.match", getName());
+        checkArgument(
+            (getLink() != null && getHtml() == null) || (getLink() == null && getHtml() != null),
+            "commentlink.%s must have either link or html",
+            getName());
+      }
+      return autoBuild();
+    }
+
+    protected abstract StoredCommentLinkInfo autoBuild();
+
+    protected abstract String getName();
+
+    protected abstract String getMatch();
+
+    protected abstract String getLink();
+
+    protected abstract String getHtml();
+
+    protected abstract boolean getOverrideOnly();
+  }
+}
diff --git a/java/com/google/gerrit/server/restapi/change/Mergeable.java b/java/com/google/gerrit/server/restapi/change/Mergeable.java
index b84b5e3..6fccdd1 100644
--- a/java/com/google/gerrit/server/restapi/change/Mergeable.java
+++ b/java/com/google/gerrit/server/restapi/change/Mergeable.java
@@ -41,6 +41,7 @@
 import com.google.inject.Inject;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.Future;
@@ -118,8 +119,9 @@
         BranchOrderSection branchOrder = projectState.getBranchOrderSection();
         if (branchOrder != null) {
           int prefixLen = Constants.R_HEADS.length();
-          String[] names = branchOrder.getMoreStable(ref.getName());
-          Map<String, Ref> refs = git.getRefDatabase().exactRef(names);
+          List<String> names = branchOrder.getMoreStable(ref.getName());
+          Map<String, Ref> refs =
+              git.getRefDatabase().exactRef(names.toArray(new String[names.size()]));
           for (String n : names) {
             Ref other = refs.get(n);
             if (other == null) {
diff --git a/java/com/google/gerrit/server/schema/SchemaCreatorImpl.java b/java/com/google/gerrit/server/schema/SchemaCreatorImpl.java
index 78fa5bd..1279218 100644
--- a/java/com/google/gerrit/server/schema/SchemaCreatorImpl.java
+++ b/java/com/google/gerrit/server/schema/SchemaCreatorImpl.java
@@ -212,7 +212,7 @@
 
   private GroupReference createGroupReference(String name) {
     AccountGroup.UUID groupUuid = GroupUuid.make(name, serverUser);
-    return new GroupReference(groupUuid, name);
+    return GroupReference.create(groupUuid, name);
   }
 
   private InternalGroupCreation getGroupCreation(Sequences seqs, GroupReference groupReference) {
diff --git a/java/com/google/gerrit/server/submit/SubscriptionGraph.java b/java/com/google/gerrit/server/submit/SubscriptionGraph.java
index 406d878..eac6d2c 100644
--- a/java/com/google/gerrit/server/submit/SubscriptionGraph.java
+++ b/java/com/google/gerrit/server/submit/SubscriptionGraph.java
@@ -16,6 +16,7 @@
 
 import static com.google.gerrit.server.project.ProjectCache.illegalState;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.ImmutableSetMultimap;
 import com.google.common.collect.MultimapBuilder;
@@ -38,11 +39,11 @@
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
-import org.eclipse.jgit.transport.RefSpec;
 
 /**
  * A container which stores subscription relationship. A SubscriptionGraph is calculated every time
@@ -270,55 +271,18 @@
 
     private Collection<BranchNameKey> getDestinationBranches(BranchNameKey src, SubscribeSection s)
         throws IOException {
-      Collection<BranchNameKey> ret = new HashSet<>();
-      logger.atFine().log("Inspecting SubscribeSection %s", s);
-      for (RefSpec r : s.getMatchingRefSpecs()) {
-        logger.atFine().log("Inspecting [matching] ref %s", r);
-        if (!r.matchSource(src.branch())) {
-          continue;
-        }
-        if (r.isWildcard()) {
-          // refs/heads/*[:refs/somewhere/*]
-          ret.add(
-              BranchNameKey.create(
-                  s.getProject(), r.expandFromSource(src.branch()).getDestination()));
-        } else {
-          // e.g. refs/heads/master[:refs/heads/stable]
-          String dest = r.getDestination();
-          if (dest == null) {
-            dest = r.getSource();
-          }
-          ret.add(BranchNameKey.create(s.getProject(), dest));
-        }
+      OpenRepo or;
+      try {
+        or = orm.getRepo(s.project());
+      } catch (NoSuchProjectException e) {
+        // A project listed a non existent project to be allowed
+        // to subscribe to it. Allow this for now, i.e. no exception is
+        // thrown.
+        return s.getDestinationBranches(src, ImmutableList.of());
       }
 
-      for (RefSpec r : s.getMultiMatchRefSpecs()) {
-        logger.atFine().log("Inspecting [all] ref %s", r);
-        if (!r.matchSource(src.branch())) {
-          continue;
-        }
-        OpenRepo or;
-        try {
-          or = orm.getRepo(s.getProject());
-        } catch (NoSuchProjectException e) {
-          // A project listed a non existent project to be allowed
-          // to subscribe to it. Allow this for now, i.e. no exception is
-          // thrown.
-          continue;
-        }
-
-        for (Ref ref : or.repo.getRefDatabase().getRefsByPrefix(RefNames.REFS_HEADS)) {
-          if (r.getDestination() != null && !r.matchDestination(ref.getName())) {
-            continue;
-          }
-          BranchNameKey b = BranchNameKey.create(s.getProject(), ref.getName());
-          if (!ret.contains(b)) {
-            ret.add(b);
-          }
-        }
-      }
-      logger.atFine().log("Returning possible branches: %s for project %s", ret, s.getProject());
-      return ret;
+      List<Ref> refs = or.repo.getRefDatabase().getRefsByPrefix(RefNames.REFS_HEADS);
+      return s.getDestinationBranches(src, refs);
     }
 
     private Collection<SubmoduleSubscription> superProjectSubscriptionsForSubmoduleBranch(
diff --git a/javatests/com/google/gerrit/acceptance/api/accounts/AgreementsIT.java b/javatests/com/google/gerrit/acceptance/api/accounts/AgreementsIT.java
index 11ca391..11cc82f 100644
--- a/javatests/com/google/gerrit/acceptance/api/accounts/AgreementsIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/accounts/AgreementsIT.java
@@ -81,7 +81,7 @@
     GroupApi groupApi = gApi.groups().id(g.get());
     groupApi.description("CLA test group");
     InternalGroup caGroup = group(AccountGroup.uuid(groupApi.detail().id));
-    GroupReference groupRef = new GroupReference(caGroup.getGroupUUID(), caGroup.getName());
+    GroupReference groupRef = GroupReference.create(caGroup.getGroupUUID(), caGroup.getName());
     PermissionRule rule = new PermissionRule(groupRef);
     rule.setAction(PermissionRule.Action.ALLOW);
     if (autoVerify) {
diff --git a/javatests/com/google/gerrit/acceptance/api/project/ProjectIT.java b/javatests/com/google/gerrit/acceptance/api/project/ProjectIT.java
index 8dc76dd..cb22849 100644
--- a/javatests/com/google/gerrit/acceptance/api/project/ProjectIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/project/ProjectIT.java
@@ -64,7 +64,6 @@
 import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
 import com.google.gerrit.server.config.ProjectConfigEntry;
 import com.google.gerrit.server.group.SystemGroupBackend;
-import com.google.gerrit.server.project.CommentLinkInfoImpl;
 import com.google.gerrit.server.project.ProjectConfig;
 import com.google.inject.AbstractModule;
 import com.google.inject.Inject;
@@ -916,7 +915,11 @@
   }
 
   private CommentLinkInfo commentLinkInfo(String name, String match, String link) {
-    return new CommentLinkInfoImpl(name, match, link, null /*html*/, null /*enabled*/);
+    CommentLinkInfo info = new CommentLinkInfo();
+    info.name = name;
+    info.match = match;
+    info.link = link;
+    return info;
   }
 
   private void assertCommentLinks(ConfigInfo actual, Map<String, CommentLinkInfo> expected) {
diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
index dd13643..da92381 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
@@ -93,6 +93,7 @@
 import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
 import com.google.gerrit.extensions.webui.PatchSetWebLink;
 import com.google.gerrit.server.change.RevisionResource;
+import com.google.gerrit.server.git.BranchOrderSection;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gerrit.server.restapi.change.GetRevisionActions;
 import com.google.inject.Inject;
@@ -1296,8 +1297,25 @@
     assertThat(changes).hasSize(1);
     assertThat(changes.get(0).changeId).isEqualTo(r2.getChangeId());
     assertThat(changes.get(0).mergeable).isEqualTo(Boolean.TRUE);
+  }
 
-    // TODO(dborowitz): Test for other-branches.
+  @Test
+  public void mergeableOtherBranches() throws Exception {
+    String head = getHead(repo(), HEAD).name();
+    createBranchWithRevision(BranchNameKey.create(project, "mergeable-other-branch"), head);
+    createBranchWithRevision(BranchNameKey.create(project, "ignored"), head);
+    PushOneCommit.Result change1 = createChange();
+    try (ProjectConfigUpdate u = updateProject(project)) {
+      u.getConfig()
+          .setBranchOrderSection(
+              BranchOrderSection.create(
+                  ImmutableList.of("master", "nonexistent", "mergeable-other-branch")));
+      u.save();
+    }
+
+    MergeableInfo mergeableInfo =
+        gApi.changes().id(change1.getChangeId()).current().mergeableOtherBranches();
+    assertThat(mergeableInfo.mergeableInto).containsExactly("mergeable-other-branch");
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/acceptance/git/AbstractSubmoduleSubscription.java b/javatests/com/google/gerrit/acceptance/git/AbstractSubmoduleSubscription.java
index a0725c3..df21625 100644
--- a/javatests/com/google/gerrit/acceptance/git/AbstractSubmoduleSubscription.java
+++ b/javatests/com/google/gerrit/acceptance/git/AbstractSubmoduleSubscription.java
@@ -204,12 +204,12 @@
       throws Exception {
     try (MetaDataUpdate md = metaDataUpdateFactory.create(submodule)) {
       md.setMessage("Added superproject subscription");
-      SubscribeSection s;
+      SubscribeSection.Builder s;
       ProjectConfig pc = projectConfigFactory.read(md);
       if (pc.getSubscribeSections().containsKey(superproject)) {
-        s = pc.getSubscribeSections().get(superproject);
+        s = pc.getSubscribeSections().get(superproject).toBuilder();
       } else {
-        s = new SubscribeSection(superproject);
+        s = SubscribeSection.builder(superproject);
       }
       String refspec;
       if (superBranch == null) {
@@ -222,7 +222,7 @@
       } else {
         s.addMultiMatchRefSpec(refspec);
       }
-      pc.addSubscribeSection(s);
+      pc.addSubscribeSection(s.build());
       ObjectId oldId = pc.getRevision();
       ObjectId newId = pc.commit(md);
       assertThat(newId).isNotEqualTo(oldId);
diff --git a/javatests/com/google/gerrit/common/data/GroupReferenceTest.java b/javatests/com/google/gerrit/common/data/GroupReferenceTest.java
index 25b55c7..113bd77 100644
--- a/javatests/com/google/gerrit/common/data/GroupReferenceTest.java
+++ b/javatests/com/google/gerrit/common/data/GroupReferenceTest.java
@@ -58,7 +58,7 @@
   public void create() {
     AccountGroup.UUID uuid = AccountGroup.uuid("uuid");
     String name = "foo";
-    GroupReference groupReference = new GroupReference(uuid, name);
+    GroupReference groupReference = GroupReference.create(uuid, name);
     assertThat(groupReference.getUUID()).isEqualTo(uuid);
     assertThat(groupReference.getName()).isEqualTo(name);
   }
@@ -68,7 +68,7 @@
     // GroupReferences where the UUID is null are used to represent groups from project.config that
     // cannot be resolved.
     String name = "foo";
-    GroupReference groupReference = new GroupReference(name);
+    GroupReference groupReference = GroupReference.create(name);
     assertThat(groupReference.getUUID()).isNull();
     assertThat(groupReference.getName()).isEqualTo(name);
   }
@@ -76,7 +76,7 @@
   @Test
   public void cannotCreateWithoutName() {
     assertThrows(
-        NullPointerException.class, () -> new GroupReference(AccountGroup.uuid("uuid"), null));
+        NullPointerException.class, () -> GroupReference.create(AccountGroup.uuid("uuid"), null));
   }
 
   @Test
@@ -98,40 +98,9 @@
   }
 
   @Test
-  public void getAndSetUuid() {
-    AccountGroup.UUID uuid = AccountGroup.uuid("uuid-foo");
-    String name = "foo";
-    GroupReference groupReference = new GroupReference(uuid, name);
-    assertThat(groupReference.getUUID()).isEqualTo(uuid);
-
-    AccountGroup.UUID uuid2 = AccountGroup.uuid("uuid-bar");
-    groupReference.setUUID(uuid2);
-    assertThat(groupReference.getUUID()).isEqualTo(uuid2);
-
-    // GroupReferences where the UUID is null are used to represent groups from project.config that
-    // cannot be resolved.
-    groupReference.setUUID(null);
-    assertThat(groupReference.getUUID()).isNull();
-  }
-
-  @Test
-  public void getAndSetName() {
-    AccountGroup.UUID uuid = AccountGroup.uuid("uuid-foo");
-    String name = "foo";
-    GroupReference groupReference = new GroupReference(uuid, name);
-    assertThat(groupReference.getName()).isEqualTo(name);
-
-    String name2 = "bar";
-    groupReference.setName(name2);
-    assertThat(groupReference.getName()).isEqualTo(name2);
-
-    assertThrows(NullPointerException.class, () -> groupReference.setName(null));
-  }
-
-  @Test
   public void toConfigValue() {
     String name = "foo";
-    GroupReference groupReference = new GroupReference(AccountGroup.uuid("uuid-foo"), name);
+    GroupReference groupReference = GroupReference.create(AccountGroup.uuid("uuid-foo"), name);
     assertThat(groupReference.toConfigValue()).isEqualTo("group " + name);
   }
 
@@ -142,9 +111,9 @@
     String name1 = "foo";
     String name2 = "bar";
 
-    GroupReference groupReference1 = new GroupReference(uuid1, name1);
-    GroupReference groupReference2 = new GroupReference(uuid1, name2);
-    GroupReference groupReference3 = new GroupReference(uuid2, name1);
+    GroupReference groupReference1 = GroupReference.create(uuid1, name1);
+    GroupReference groupReference2 = GroupReference.create(uuid1, name2);
+    GroupReference groupReference3 = GroupReference.create(uuid2, name1);
 
     assertThat(groupReference1.equals(groupReference2)).isTrue();
     assertThat(groupReference1.equals(groupReference3)).isFalse();
@@ -154,10 +123,10 @@
   @Test
   public void testHashcode() {
     AccountGroup.UUID uuid1 = AccountGroup.uuid("uuid1");
-    assertThat(new GroupReference(uuid1, "foo").hashCode())
-        .isEqualTo(new GroupReference(uuid1, "bar").hashCode());
+    assertThat(GroupReference.create(uuid1, "foo").hashCode())
+        .isEqualTo(GroupReference.create(uuid1, "bar").hashCode());
 
     // Check that the following calls don't fail with an exception.
-    new GroupReference("bar").hashCode();
+    GroupReference.create("bar").hashCode();
   }
 }
diff --git a/javatests/com/google/gerrit/common/data/PermissionRuleTest.java b/javatests/com/google/gerrit/common/data/PermissionRuleTest.java
index d815dbc..6dc357c 100644
--- a/javatests/com/google/gerrit/common/data/PermissionRuleTest.java
+++ b/javatests/com/google/gerrit/common/data/PermissionRuleTest.java
@@ -28,7 +28,7 @@
 
   @Before
   public void setup() {
-    this.groupReference = new GroupReference(AccountGroup.uuid("uuid"), "group");
+    this.groupReference = GroupReference.create(AccountGroup.uuid("uuid"), "group");
     this.permissionRule = new PermissionRule(groupReference);
   }
 
@@ -130,7 +130,7 @@
 
   @Test
   public void setGroup() {
-    GroupReference groupReference2 = new GroupReference(AccountGroup.uuid("uuid2"), "group2");
+    GroupReference groupReference2 = GroupReference.create(AccountGroup.uuid("uuid2"), "group2");
     assertThat(groupReference2).isNotEqualTo(groupReference);
 
     assertThat(permissionRule.getGroup()).isEqualTo(groupReference);
@@ -141,10 +141,10 @@
 
   @Test
   public void mergeFromAnyBlock() {
-    GroupReference groupReference1 = new GroupReference(AccountGroup.uuid("uuid1"), "group1");
+    GroupReference groupReference1 = GroupReference.create(AccountGroup.uuid("uuid1"), "group1");
     PermissionRule permissionRule1 = new PermissionRule(groupReference1);
 
-    GroupReference groupReference2 = new GroupReference(AccountGroup.uuid("uuid2"), "group2");
+    GroupReference groupReference2 = GroupReference.create(AccountGroup.uuid("uuid2"), "group2");
     PermissionRule permissionRule2 = new PermissionRule(groupReference2);
 
     permissionRule1.mergeFrom(permissionRule2);
@@ -169,10 +169,10 @@
 
   @Test
   public void mergeFromAnyDeny() {
-    GroupReference groupReference1 = new GroupReference(AccountGroup.uuid("uuid1"), "group1");
+    GroupReference groupReference1 = GroupReference.create(AccountGroup.uuid("uuid1"), "group1");
     PermissionRule permissionRule1 = new PermissionRule(groupReference1);
 
-    GroupReference groupReference2 = new GroupReference(AccountGroup.uuid("uuid2"), "group2");
+    GroupReference groupReference2 = GroupReference.create(AccountGroup.uuid("uuid2"), "group2");
     PermissionRule permissionRule2 = new PermissionRule(groupReference2);
 
     permissionRule1.mergeFrom(permissionRule2);
@@ -192,10 +192,10 @@
 
   @Test
   public void mergeFromAnyBatch() {
-    GroupReference groupReference1 = new GroupReference(AccountGroup.uuid("uuid1"), "group1");
+    GroupReference groupReference1 = GroupReference.create(AccountGroup.uuid("uuid1"), "group1");
     PermissionRule permissionRule1 = new PermissionRule(groupReference1);
 
-    GroupReference groupReference2 = new GroupReference(AccountGroup.uuid("uuid2"), "group2");
+    GroupReference groupReference2 = GroupReference.create(AccountGroup.uuid("uuid2"), "group2");
     PermissionRule permissionRule2 = new PermissionRule(groupReference2);
 
     permissionRule1.mergeFrom(permissionRule2);
@@ -215,10 +215,10 @@
 
   @Test
   public void mergeFromAnyForce() {
-    GroupReference groupReference1 = new GroupReference(AccountGroup.uuid("uuid1"), "group1");
+    GroupReference groupReference1 = GroupReference.create(AccountGroup.uuid("uuid1"), "group1");
     PermissionRule permissionRule1 = new PermissionRule(groupReference1);
 
-    GroupReference groupReference2 = new GroupReference(AccountGroup.uuid("uuid2"), "group2");
+    GroupReference groupReference2 = GroupReference.create(AccountGroup.uuid("uuid2"), "group2");
     PermissionRule permissionRule2 = new PermissionRule(groupReference2);
 
     permissionRule1.mergeFrom(permissionRule2);
@@ -238,11 +238,11 @@
 
   @Test
   public void mergeFromMergeRange() {
-    GroupReference groupReference1 = new GroupReference(AccountGroup.uuid("uuid1"), "group1");
+    GroupReference groupReference1 = GroupReference.create(AccountGroup.uuid("uuid1"), "group1");
     PermissionRule permissionRule1 = new PermissionRule(groupReference1);
     permissionRule1.setRange(-1, 2);
 
-    GroupReference groupReference2 = new GroupReference(AccountGroup.uuid("uuid2"), "group2");
+    GroupReference groupReference2 = GroupReference.create(AccountGroup.uuid("uuid2"), "group2");
     PermissionRule permissionRule2 = new PermissionRule(groupReference2);
     permissionRule2.setRange(-2, 1);
 
@@ -255,10 +255,10 @@
 
   @Test
   public void mergeFromGroupNotChanged() {
-    GroupReference groupReference1 = new GroupReference(AccountGroup.uuid("uuid1"), "group1");
+    GroupReference groupReference1 = GroupReference.create(AccountGroup.uuid("uuid1"), "group1");
     PermissionRule permissionRule1 = new PermissionRule(groupReference1);
 
-    GroupReference groupReference2 = new GroupReference(AccountGroup.uuid("uuid2"), "group2");
+    GroupReference groupReference2 = GroupReference.create(AccountGroup.uuid("uuid2"), "group2");
     PermissionRule permissionRule2 = new PermissionRule(groupReference2);
 
     permissionRule1.mergeFrom(permissionRule2);
@@ -347,7 +347,7 @@
 
   @Test
   public void testEquals() {
-    GroupReference groupReference2 = new GroupReference(AccountGroup.uuid("uuid2"), "group2");
+    GroupReference groupReference2 = GroupReference.create(AccountGroup.uuid("uuid2"), "group2");
     PermissionRule permissionRuleOther = new PermissionRule(groupReference2);
     assertThat(permissionRule.equals(permissionRuleOther)).isFalse();
 
diff --git a/javatests/com/google/gerrit/common/data/PermissionTest.java b/javatests/com/google/gerrit/common/data/PermissionTest.java
index 1012eff..ef36ad9 100644
--- a/javatests/com/google/gerrit/common/data/PermissionTest.java
+++ b/javatests/com/google/gerrit/common/data/PermissionTest.java
@@ -154,14 +154,14 @@
   @Test
   public void setAndGetRules() {
     PermissionRule permissionRule1 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-1"), "group1"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-1"), "group1"));
     PermissionRule permissionRule2 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-2"), "group2"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-2"), "group2"));
     permission.setRules(ImmutableList.of(permissionRule1, permissionRule2));
     assertThat(permission.getRules()).containsExactly(permissionRule1, permissionRule2).inOrder();
 
     PermissionRule permissionRule3 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-3"), "group3"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-3"), "group3"));
     permission.setRules(ImmutableList.of(permissionRule3));
     assertThat(permission.getRules()).containsExactly(permissionRule3);
   }
@@ -169,10 +169,10 @@
   @Test
   public void cannotAddPermissionByModifyingListThatWasProvidedToAccessSection() {
     PermissionRule permissionRule1 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-1"), "group1"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-1"), "group1"));
     PermissionRule permissionRule2 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-2"), "group2"));
-    GroupReference groupReference3 = new GroupReference(AccountGroup.uuid("uuid-3"), "group3");
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-2"), "group2"));
+    GroupReference groupReference3 = GroupReference.create(AccountGroup.uuid("uuid-3"), "group3");
 
     List<PermissionRule> rules = new ArrayList<>();
     rules.add(permissionRule1);
@@ -187,14 +187,14 @@
 
   @Test
   public void getNonExistingRule() {
-    GroupReference groupReference = new GroupReference(AccountGroup.uuid("uuid-1"), "group1");
+    GroupReference groupReference = GroupReference.create(AccountGroup.uuid("uuid-1"), "group1");
     assertThat(permission.getRule(groupReference)).isNull();
     assertThat(permission.getRule(groupReference, false)).isNull();
   }
 
   @Test
   public void getRule() {
-    GroupReference groupReference = new GroupReference(AccountGroup.uuid("uuid-1"), "group1");
+    GroupReference groupReference = GroupReference.create(AccountGroup.uuid("uuid-1"), "group1");
     PermissionRule permissionRule = new PermissionRule(groupReference);
     permission.setRules(ImmutableList.of(permissionRule));
     assertThat(permission.getRule(groupReference)).isEqualTo(permissionRule);
@@ -202,7 +202,7 @@
 
   @Test
   public void createMissingRuleOnGet() {
-    GroupReference groupReference = new GroupReference(AccountGroup.uuid("uuid-1"), "group1");
+    GroupReference groupReference = GroupReference.create(AccountGroup.uuid("uuid-1"), "group1");
     assertThat(permission.getRule(groupReference)).isNull();
 
     assertThat(permission.getRule(groupReference, true))
@@ -212,11 +212,11 @@
   @Test
   public void addRule() {
     PermissionRule permissionRule1 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-1"), "group1"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-1"), "group1"));
     PermissionRule permissionRule2 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-2"), "group2"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-2"), "group2"));
     permission.setRules(ImmutableList.of(permissionRule1, permissionRule2));
-    GroupReference groupReference3 = new GroupReference(AccountGroup.uuid("uuid-3"), "group3");
+    GroupReference groupReference3 = GroupReference.create(AccountGroup.uuid("uuid-3"), "group3");
     assertThat(permission.getRule(groupReference3)).isNull();
 
     PermissionRule permissionRule3 = new PermissionRule(groupReference3);
@@ -230,10 +230,10 @@
   @Test
   public void removeRule() {
     PermissionRule permissionRule1 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-1"), "group1"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-1"), "group1"));
     PermissionRule permissionRule2 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-2"), "group2"));
-    GroupReference groupReference3 = new GroupReference(AccountGroup.uuid("uuid-3"), "group3");
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-2"), "group2"));
+    GroupReference groupReference3 = GroupReference.create(AccountGroup.uuid("uuid-3"), "group3");
     PermissionRule permissionRule3 = new PermissionRule(groupReference3);
 
     permission.setRules(ImmutableList.of(permissionRule1, permissionRule2, permissionRule3));
@@ -247,10 +247,10 @@
   @Test
   public void removeRuleByGroupReference() {
     PermissionRule permissionRule1 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-1"), "group1"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-1"), "group1"));
     PermissionRule permissionRule2 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-2"), "group2"));
-    GroupReference groupReference3 = new GroupReference(AccountGroup.uuid("uuid-3"), "group3");
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-2"), "group2"));
+    GroupReference groupReference3 = GroupReference.create(AccountGroup.uuid("uuid-3"), "group3");
     PermissionRule permissionRule3 = new PermissionRule(groupReference3);
 
     permission.setRules(ImmutableList.of(permissionRule1, permissionRule2, permissionRule3));
@@ -264,9 +264,9 @@
   @Test
   public void clearRules() {
     PermissionRule permissionRule1 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-1"), "group1"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-1"), "group1"));
     PermissionRule permissionRule2 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-2"), "group2"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-2"), "group2"));
 
     permission.setRules(ImmutableList.of(permissionRule1, permissionRule2));
     assertThat(permission.getRules()).isNotEmpty();
@@ -278,11 +278,11 @@
   @Test
   public void mergePermissions() {
     PermissionRule permissionRule1 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-1"), "group1"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-1"), "group1"));
     PermissionRule permissionRule2 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-2"), "group2"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-2"), "group2"));
     PermissionRule permissionRule3 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-3"), "group3"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-3"), "group3"));
 
     Permission permission1 = new Permission("foo");
     permission1.setRules(ImmutableList.of(permissionRule1, permissionRule2));
@@ -299,9 +299,9 @@
   @Test
   public void testEquals() {
     PermissionRule permissionRule1 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-1"), "group1"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-1"), "group1"));
     PermissionRule permissionRule2 =
-        new PermissionRule(new GroupReference(AccountGroup.uuid("uuid-2"), "group2"));
+        new PermissionRule(GroupReference.create(AccountGroup.uuid("uuid-2"), "group2"));
 
     permission.setRules(ImmutableList.of(permissionRule1, permissionRule2));
 
diff --git a/javatests/com/google/gerrit/server/account/DestinationListTest.java b/javatests/com/google/gerrit/server/account/DestinationListTest.java
index 4188f39..6fcf75c 100644
--- a/javatests/com/google/gerrit/server/account/DestinationListTest.java
+++ b/javatests/com/google/gerrit/server/account/DestinationListTest.java
@@ -132,7 +132,7 @@
     List<ValidationError> errors = new ArrayList<>();
     new DestinationList().parseLabel(LABEL, L_BAD, errors::add);
     assertThat(errors)
-        .containsExactly(new ValidationError("destinationslabel", 1, "missing tab delimiter"));
+        .containsExactly(ValidationError.create("destinationslabel", 1, "missing tab delimiter"));
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/server/account/QueryListTest.java b/javatests/com/google/gerrit/server/account/QueryListTest.java
index 7d491c9..74ce907 100644
--- a/javatests/com/google/gerrit/server/account/QueryListTest.java
+++ b/javatests/com/google/gerrit/server/account/QueryListTest.java
@@ -101,7 +101,8 @@
   public void testParseBad() throws Exception {
     List<ValidationError> errors = new ArrayList<>();
     assertThat(QueryList.parse(L_BAD, errors::add).asText()).isNull();
-    assertThat(errors).containsExactly(new ValidationError("queries", 1, "missing tab delimiter"));
+    assertThat(errors)
+        .containsExactly(ValidationError.create("queries", 1, "missing tab delimiter"));
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/server/group/db/GroupNameNotesTest.java b/javatests/com/google/gerrit/server/group/db/GroupNameNotesTest.java
index df97e88..278f617 100644
--- a/javatests/com/google/gerrit/server/group/db/GroupNameNotesTest.java
+++ b/javatests/com/google/gerrit/server/group/db/GroupNameNotesTest.java
@@ -393,8 +393,8 @@
 
     ImmutableList<GroupReference> allGroups = GroupNameNotes.loadAllGroups(repo);
 
-    GroupReference group1 = new GroupReference(groupUuid1, groupName1.get());
-    GroupReference group2 = new GroupReference(groupUuid2, groupName2.get());
+    GroupReference group1 = GroupReference.create(groupUuid1, groupName1.get());
+    GroupReference group2 = GroupReference.create(groupUuid2, groupName2.get());
     assertThat(allGroups).containsExactly(group1, group2);
   }
 
@@ -406,8 +406,8 @@
 
     ImmutableList<GroupReference> allGroups = GroupNameNotes.loadAllGroups(repo);
 
-    GroupReference group1 = new GroupReference(groupUuid, groupName.get());
-    GroupReference group2 = new GroupReference(groupUuid, anotherGroupName.get());
+    GroupReference group1 = GroupReference.create(groupUuid, groupName.get());
+    GroupReference group2 = GroupReference.create(groupUuid, anotherGroupName.get());
     assertThat(allGroups).containsExactly(group1, group2);
   }
 
@@ -498,14 +498,14 @@
   @Test
   public void updateGroupNamesRejectsNonOneToOneGroupReferences() throws Exception {
     assertIllegalArgument(
-        new GroupReference(AccountGroup.uuid("uuid1"), "name1"),
-        new GroupReference(AccountGroup.uuid("uuid1"), "name2"));
+        GroupReference.create(AccountGroup.uuid("uuid1"), "name1"),
+        GroupReference.create(AccountGroup.uuid("uuid1"), "name2"));
     assertIllegalArgument(
-        new GroupReference(AccountGroup.uuid("uuid1"), "name1"),
-        new GroupReference(AccountGroup.uuid("uuid2"), "name1"));
+        GroupReference.create(AccountGroup.uuid("uuid1"), "name1"),
+        GroupReference.create(AccountGroup.uuid("uuid2"), "name1"));
     assertIllegalArgument(
-        new GroupReference(AccountGroup.uuid("uuid1"), "name1"),
-        new GroupReference(AccountGroup.uuid("uuid1"), "name1"));
+        GroupReference.create(AccountGroup.uuid("uuid1"), "name1"),
+        GroupReference.create(AccountGroup.uuid("uuid1"), "name1"));
   }
 
   @Test
@@ -554,7 +554,7 @@
 
   private GroupReference newGroup(String name) {
     int id = idCounter.incrementAndGet();
-    return new GroupReference(AccountGroup.uuid(name + "-" + id), name);
+    return GroupReference.create(AccountGroup.uuid(name + "-" + id), name);
   }
 
   private static PersonIdent newPersonIdent() {
diff --git a/javatests/com/google/gerrit/server/project/GroupListTest.java b/javatests/com/google/gerrit/server/project/GroupListTest.java
index 518f85d..18e1631 100644
--- a/javatests/com/google/gerrit/server/project/GroupListTest.java
+++ b/javatests/com/google/gerrit/server/project/GroupListTest.java
@@ -63,7 +63,7 @@
   @Test
   public void put() {
     AccountGroup.UUID uuid = AccountGroup.uuid("abc");
-    GroupReference groupReference = new GroupReference(uuid, "Hutzliputz");
+    GroupReference groupReference = GroupReference.create(uuid, "Hutzliputz");
 
     groupList.put(uuid, groupReference);
 
@@ -78,7 +78,7 @@
 
     assertEquals(2, result.size());
     AccountGroup.UUID uuid = AccountGroup.uuid("ebe31c01aec2c9ac3b3c03e87a47450829ff4310");
-    GroupReference expected = new GroupReference(uuid, "Administrators");
+    GroupReference expected = GroupReference.create(uuid, "Administrators");
 
     assertTrue(result.contains(expected));
   }
diff --git a/javatests/com/google/gerrit/server/project/ProjectConfigTest.java b/javatests/com/google/gerrit/server/project/ProjectConfigTest.java
index 0dd6436..214aae7 100644
--- a/javatests/com/google/gerrit/server/project/ProjectConfigTest.java
+++ b/javatests/com/google/gerrit/server/project/ProjectConfigTest.java
@@ -34,6 +34,7 @@
 import com.google.gerrit.server.config.PluginConfig;
 import com.google.gerrit.server.config.SitePaths;
 import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
+import com.google.gerrit.server.git.BranchOrderSection;
 import com.google.gerrit.server.git.ValidationError;
 import com.google.gerrit.server.git.meta.MetaDataUpdate;
 import com.google.gerrit.server.project.testing.TestLabels;
@@ -90,8 +91,8 @@
   @Rule public TemporaryFolder temporaryFolder = new TemporaryFolder();
 
   private final GroupReference developers =
-      new GroupReference(AccountGroup.uuid("X"), "Developers");
-  private final GroupReference staff = new GroupReference(AccountGroup.uuid("Y"), "Staff");
+      GroupReference.create(AccountGroup.uuid("X"), "Developers");
+  private final GroupReference staff = GroupReference.create(AccountGroup.uuid("Y"), "Staff");
 
   private SitePaths sitePaths;
   private ProjectConfig.Factory factory;
@@ -361,12 +362,43 @@
   }
 
   @Test
+  public void readExistingBranchOrder() throws Exception {
+    RevCommit rev =
+        tr.commit()
+            .add("project.config", "[branchOrder]\n" + "\tbranch = foo\n" + "\tbranch = bar\n")
+            .create();
+    update(rev);
+
+    ProjectConfig cfg = read(rev);
+    assertThat(cfg.getBranchOrderSection())
+        .isEqualTo(BranchOrderSection.create(ImmutableList.of("foo", "bar")));
+  }
+
+  @Test
+  public void editBranchOrder() throws Exception {
+    RevCommit rev = tr.commit().create();
+    update(rev);
+
+    ProjectConfig cfg = read(rev);
+    cfg.setBranchOrderSection(BranchOrderSection.create(ImmutableList.of("foo", "bar")));
+    rev = commit(cfg);
+    assertThat(text(rev, "project.config"))
+        .isEqualTo("[branchOrder]\n" + "\tbranch = foo\n" + "\tbranch = bar\n");
+  }
+
+  @Test
   public void addCommentLink() throws Exception {
     RevCommit rev = tr.commit().create();
     update(rev);
 
     ProjectConfig cfg = read(rev);
-    CommentLinkInfoImpl cm = new CommentLinkInfoImpl("Test", "abc.*", null, "<a>link</a>", true);
+    StoredCommentLinkInfo cm =
+        StoredCommentLinkInfo.builder("Test")
+            .setMatch("abc.*")
+            .setHtml("<a>link</a>")
+            .setEnabled(true)
+            .setOverrideOnly(false)
+            .build();
     cfg.addCommentLinkSection(cm);
     rev = commit(cfg);
     assertThat(text(rev, "project.config"))
@@ -529,12 +561,11 @@
     ProjectConfig cfg = read(rev);
     assertThat(cfg.getCommentLinkSections())
         .containsExactly(
-            new CommentLinkInfoImpl(
-                "bugzilla",
-                "(bug\\s+#?)(\\d+)",
-                "http://bugs.example.com/show_bug.cgi?id=$2",
-                null,
-                null));
+            StoredCommentLinkInfo.builder("bugzilla")
+                .setMatch("(bug\\s+#?)(\\d+)")
+                .setLink("http://bugs.example.com/show_bug.cgi?id=$2")
+                .setOverrideOnly(false)
+                .build());
   }
 
   @Test
@@ -543,7 +574,7 @@
         tr.commit().add("project.config", "[commentlink \"bugzilla\"]\n \tenabled = true").create();
     ProjectConfig cfg = read(rev);
     assertThat(cfg.getCommentLinkSections())
-        .containsExactly(new CommentLinkInfoImpl.Enabled("bugzilla"));
+        .containsExactly(StoredCommentLinkInfo.enabled("bugzilla"));
   }
 
   @Test
@@ -554,7 +585,7 @@
             .create();
     ProjectConfig cfg = read(rev);
     assertThat(cfg.getCommentLinkSections())
-        .containsExactly(new CommentLinkInfoImpl.Disabled("bugzilla"));
+        .containsExactly(StoredCommentLinkInfo.disabled("bugzilla"));
   }
 
   @Test
@@ -571,7 +602,7 @@
     assertThat(cfg.getCommentLinkSections()).isEmpty();
     assertThat(cfg.getValidationErrors())
         .containsExactly(
-            new ValidationError(
+            ValidationError.create(
                 "project.config: Invalid pattern \"(bugs{+#?)(d+)\" in commentlink.bugzilla.match: "
                     + "Illegal repetition near index 4\n"
                     + "(bugs{+#?)(d+)\n"
@@ -592,7 +623,7 @@
     assertThat(cfg.getCommentLinkSections()).isEmpty();
     assertThat(cfg.getValidationErrors())
         .containsExactly(
-            new ValidationError(
+            ValidationError.create(
                 "project.config: Error in pattern \"(bugs#?)(d+)\" in commentlink.bugzilla.match: "
                     + "Raw html replacement not allowed"));
   }
@@ -607,7 +638,7 @@
     assertThat(cfg.getCommentLinkSections()).isEmpty();
     assertThat(cfg.getValidationErrors())
         .containsExactly(
-            new ValidationError(
+            ValidationError.create(
                 "project.config: Error in pattern \"(bugs#?)(d+)\" in commentlink.bugzilla.match: "
                     + "commentlink.bugzilla must have either link or html"));
   }
diff --git a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
index dbcac0d..331bb4c 100644
--- a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
+++ b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
@@ -1861,7 +1861,7 @@
       ProjectConfig config = projectConfigFactory.read(md);
       AccessSection s = config.getAccessSection(ref, true);
       Permission p = s.getPermission(permission, true);
-      PermissionRule rule = new PermissionRule(new GroupReference(groupUUID, groupUUID.get()));
+      PermissionRule rule = new PermissionRule(GroupReference.create(groupUUID, groupUUID.get()));
       rule.setForce(force);
       p.add(rule);
       config.commit(md);
diff --git a/javatests/com/google/gerrit/server/schema/AllProjectsCreatorTest.java b/javatests/com/google/gerrit/server/schema/AllProjectsCreatorTest.java
index b65f4d2..eceec8b 100644
--- a/javatests/com/google/gerrit/server/schema/AllProjectsCreatorTest.java
+++ b/javatests/com/google/gerrit/server/schema/AllProjectsCreatorTest.java
@@ -102,7 +102,7 @@
 
   private GroupReference createGroupReference(String name) {
     AccountGroup.UUID groupUuid = GroupUuid.make(name, serverUser);
-    return new GroupReference(groupUuid, name);
+    return GroupReference.create(groupUuid, name);
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/server/submit/SubscriptionGraphTest.java b/javatests/com/google/gerrit/server/submit/SubscriptionGraphTest.java
index dbcc209..489e1b6 100644
--- a/javatests/com/google/gerrit/server/submit/SubscriptionGraphTest.java
+++ b/javatests/com/google/gerrit/server/submit/SubscriptionGraphTest.java
@@ -193,9 +193,9 @@
   }
 
   private void allowSubscription(BranchNameKey branch) {
-    SubscribeSection s = new SubscribeSection(branch.project());
+    SubscribeSection.Builder s = SubscribeSection.builder(branch.project());
     s.addMultiMatchRefSpec("refs/heads/*:refs/heads/*");
-    when(mockProjectState.getSubscribeSections(branch)).thenReturn(ImmutableSet.of(s));
+    when(mockProjectState.getSubscribeSections(branch)).thenReturn(ImmutableSet.of(s.build()));
   }
 
   private void setSubscription(
diff --git a/plugins/singleusergroup b/plugins/singleusergroup
index d04c4c3..9eb6334 160000
--- a/plugins/singleusergroup
+++ b/plugins/singleusergroup
@@ -1 +1 @@
-Subproject commit d04c4c33ad36e2e11ccc8b798357dd1e4e979a1a
+Subproject commit 9eb63345a129533aa88235af3ba9308c53cee1d2