diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index 3f0c751..415465e 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -7488,6 +7488,13 @@
 patch set is inferred. +
 Empty string is used for rebasing directly on top of the target branch,
 which effectively breaks dependency towards a parent change.
+|`allow_conflicts`|optional, defaults to false|
+If `true`, the rebase also succeeds if there are conflicts. +
+If there are conflicts the file contents of the rebased patch set contain
+git conflict markers to indicate the conflicts. +
+Callers can find out whether there were conflicts by checking the
+`contains_git_conflicts` field in the returned link:#change-info[ChangeInfo]. +
+If there are conflicts the change is marked as work-in-progress.
 |===========================
 
 [[related-change-and-commit-info]]
diff --git a/java/com/google/gerrit/extensions/api/changes/RebaseInput.java b/java/com/google/gerrit/extensions/api/changes/RebaseInput.java
index 5f4a014..10559a3 100644
--- a/java/com/google/gerrit/extensions/api/changes/RebaseInput.java
+++ b/java/com/google/gerrit/extensions/api/changes/RebaseInput.java
@@ -16,4 +16,12 @@
 
 public class RebaseInput {
   public String base;
+
+  /**
+   * Whether the rebase should succeed if there are conflicts.
+   *
+   * <p>If there are conflicts the file contents of the rebased change contain git conflict markers
+   * to indicate the conflicts.
+   */
+  public boolean allowConflicts;
 }
diff --git a/java/com/google/gerrit/extensions/api/changes/RevisionApi.java b/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
index b419c2f..73e6a4e 100644
--- a/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
+++ b/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
@@ -68,6 +68,8 @@
 
   ChangeApi rebase(RebaseInput in) throws RestApiException;
 
+  ChangeInfo rebaseAsInfo(RebaseInput in) throws RestApiException;
+
   boolean canRebase() throws RestApiException;
 
   RevisionReviewerApi reviewer(String id) throws RestApiException;
@@ -218,6 +220,11 @@
     }
 
     @Override
+    public ChangeInfo rebaseAsInfo(RebaseInput in) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
     public boolean canRebase() throws RestApiException {
       throw new NotImplementedException();
     }
diff --git a/java/com/google/gerrit/extensions/common/ChangeInfo.java b/java/com/google/gerrit/extensions/common/ChangeInfo.java
index 190a97e..7ed2f95 100644
--- a/java/com/google/gerrit/extensions/common/ChangeInfo.java
+++ b/java/com/google/gerrit/extensions/common/ChangeInfo.java
@@ -83,7 +83,8 @@
    * com.google.gerrit.server.restapi.change.CreateChange}, {@link
    * com.google.gerrit.server.restapi.change.CreateMergePatchSet}, {@link
    * com.google.gerrit.server.restapi.change.CherryPick}, {@link
-   * com.google.gerrit.server.restapi.change.CherryPickCommit}
+   * com.google.gerrit.server.restapi.change.CherryPickCommit}, {@link
+   * com.google.gerrit.server.restapi.change.Rebase}
    */
   public Boolean containsGitConflicts;
 
diff --git a/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java b/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
index 04d2e8ae..36d48033 100644
--- a/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
+++ b/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
@@ -282,7 +282,16 @@
   @Override
   public ChangeApi rebase(RebaseInput in) throws RestApiException {
     try {
-      return changes.id(rebase.apply(revision, in).value()._number);
+      return changes.id(rebaseAsInfo(in)._number);
+    } catch (Exception e) {
+      throw asRestApiException("Cannot rebase ps", e);
+    }
+  }
+
+  @Override
+  public ChangeInfo rebaseAsInfo(RebaseInput in) throws RestApiException {
+    try {
+      return rebase.apply(revision, in).value();
     } catch (Exception e) {
       throw asRestApiException("Cannot rebase ps", e);
     }
diff --git a/java/com/google/gerrit/server/change/RebaseChangeOp.java b/java/com/google/gerrit/server/change/RebaseChangeOp.java
index 231359b..a548262 100644
--- a/java/com/google/gerrit/server/change/RebaseChangeOp.java
+++ b/java/com/google/gerrit/server/change/RebaseChangeOp.java
@@ -15,8 +15,11 @@
 package com.google.gerrit.server.change;
 
 import static com.google.common.base.Preconditions.checkState;
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
 import static com.google.gerrit.server.project.ProjectCache.illegalState;
 
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.MergeConflictException;
@@ -26,6 +29,8 @@
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.change.RebaseUtil.Base;
+import com.google.gerrit.server.git.CodeReviewCommit;
+import com.google.gerrit.server.git.CodeReviewCommit.CodeReviewRevWalk;
 import com.google.gerrit.server.git.GroupCollector;
 import com.google.gerrit.server.git.MergeUtil;
 import com.google.gerrit.server.notedb.ChangeNotes;
@@ -41,13 +46,27 @@
 import com.google.inject.Inject;
 import com.google.inject.assistedinject.Assisted;
 import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+import org.eclipse.jgit.diff.Sequence;
+import org.eclipse.jgit.dircache.DirCache;
 import org.eclipse.jgit.lib.CommitBuilder;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.merge.MergeResult;
+import org.eclipse.jgit.merge.ResolveMerger;
 import org.eclipse.jgit.merge.ThreeWayMerger;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
 
+/**
+ * BatchUpdate operation that rebases a change.
+ *
+ * <p>Can only be executed in a {@link com.google.gerrit.server.update.BatchUpdate} set has a {@link
+ * CodeReviewRevWalk} set as {@link RevWalk} (set via {@link
+ * com.google.gerrit.server.update.BatchUpdate#setRepository(org.eclipse.jgit.lib.Repository,
+ * RevWalk, org.eclipse.jgit.lib.ObjectInserter)}).
+ */
 public class RebaseChangeOp implements BatchUpdateOp {
   public interface Factory {
     RebaseChangeOp create(ChangeNotes notes, PatchSet originalPatchSet, ObjectId baseCommitId);
@@ -69,12 +88,13 @@
   private boolean validate = true;
   private boolean checkAddPatchSetPermission = true;
   private boolean forceContentMerge;
+  private boolean allowConflicts;
   private boolean detailedCommitMessage;
   private boolean postMessage = true;
   private boolean sendEmail = true;
   private boolean matchAuthorToCommitterDate = false;
 
-  private RevCommit rebasedCommit;
+  private CodeReviewCommit rebasedCommit;
   private PatchSet.Id rebasedPatchSetId;
   private PatchSetInserter patchSetInserter;
   private PatchSet rebasedPatchSet;
@@ -126,6 +146,19 @@
     return this;
   }
 
+  /**
+   * Allows the rebase to succeed if there are conflicts.
+   *
+   * <p>This setting requires that {@link #forceContentMerge} is set {@code true}. If {@link
+   * #forceContentMerge} is {@code false} this setting has no effect.
+   *
+   * @see #setForceContentMerge(boolean)
+   */
+  public RebaseChangeOp setAllowConflicts(boolean allowConflicts) {
+    this.allowConflicts = allowConflicts;
+    return this;
+  }
+
   public RebaseChangeOp setDetailedCommitMessage(boolean detailedCommitMessage) {
     this.detailedCommitMessage = detailedCommitMessage;
     return this;
@@ -186,14 +219,11 @@
             .setFireRevisionCreated(fireRevisionCreated)
             .setCheckAddPatchSetPermission(checkAddPatchSetPermission)
             .setValidate(validate)
-            .setSendEmail(sendEmail);
+            .setSendEmail(sendEmail)
+            .setWorkInProgress(!rebasedCommit.getFilesWithGitConflicts().isEmpty());
     if (postMessage) {
       patchSetInserter.setMessage(
-          "Patch Set "
-              + rebasedPatchSetId.get()
-              + ": Patch Set "
-              + originalPatchSet.id().get()
-              + " was rebased");
+          messageForRebasedChange(rebasedPatchSetId, originalPatchSet.id(), rebasedCommit));
     }
 
     if (base != null && !base.notes().getChange().isMerged()) {
@@ -208,6 +238,24 @@
     patchSetInserter.updateRepo(ctx);
   }
 
+  private static String messageForRebasedChange(
+      PatchSet.Id rebasePatchSetId, PatchSet.Id originalPatchSetId, CodeReviewCommit commit) {
+    StringBuilder stringBuilder =
+        new StringBuilder(
+            String.format(
+                "Patch Set %d: Patch Set %d was rebased",
+                rebasePatchSetId.get(), originalPatchSetId.get()));
+
+    if (!commit.getFilesWithGitConflicts().isEmpty()) {
+      stringBuilder.append("\n\nThe following files contain Git conflicts:\n");
+      commit.getFilesWithGitConflicts().stream()
+          .sorted()
+          .forEach(filePath -> stringBuilder.append("* ").append(filePath).append("\n"));
+    }
+
+    return stringBuilder.toString();
+  }
+
   @Override
   public boolean updateChange(ChangeContext ctx)
       throws ResourceConflictException, IOException, BadRequestException {
@@ -221,7 +269,7 @@
     patchSetInserter.postUpdate(ctx);
   }
 
-  public RevCommit getRebasedCommit() {
+  public CodeReviewCommit getRebasedCommit() {
     checkState(rebasedCommit != null, "getRebasedCommit() only valid after updateRepo");
     return rebasedCommit;
   }
@@ -254,7 +302,7 @@
    * @throws MergeConflictException the rebase failed due to a merge conflict.
    * @throws IOException the merge failed for another reason.
    */
-  private RevCommit rebaseCommit(
+  private CodeReviewCommit rebaseCommit(
       RepoContext ctx, RevCommit original, ObjectId base, String commitMessage)
       throws ResourceConflictException, IOException {
     RevCommit parentCommit = original.getParent(0);
@@ -266,15 +314,56 @@
     ThreeWayMerger merger =
         newMergeUtil().newThreeWayMerger(ctx.getInserter(), ctx.getRepoView().getConfig());
     merger.setBase(parentCommit);
+
+    DirCache dc = DirCache.newInCore();
+    if (allowConflicts && merger instanceof ResolveMerger) {
+      // The DirCache must be set on ResolveMerger before calling
+      // ResolveMerger#merge(AnyObjectId...) otherwise the entries in DirCache don't get populated.
+      ((ResolveMerger) merger).setDirCache(dc);
+    }
+
     boolean success = merger.merge(original, base);
 
-    if (!success || merger.getResultTreeId() == null) {
-      throw new MergeConflictException(
-          "The change could not be rebased due to a conflict during merge.");
+    ObjectId tree;
+    ImmutableSet<String> filesWithGitConflicts;
+    if (success) {
+      filesWithGitConflicts = null;
+      tree = merger.getResultTreeId();
+    } else {
+      List<String> conflicts = ImmutableList.of();
+      if (merger instanceof ResolveMerger) {
+        conflicts = ((ResolveMerger) merger).getUnmergedPaths();
+      }
+
+      if (!allowConflicts || !(merger instanceof ResolveMerger)) {
+        throw new MergeConflictException(
+            "The change could not be rebased due to a conflict during merge.\n\n"
+                + MergeUtil.createConflictMessage(conflicts));
+      }
+
+      Map<String, MergeResult<? extends Sequence>> mergeResults =
+          ((ResolveMerger) merger).getMergeResults();
+
+      filesWithGitConflicts =
+          mergeResults.entrySet().stream()
+              .filter(e -> e.getValue().containsConflicts())
+              .map(Map.Entry::getKey)
+              .collect(toImmutableSet());
+
+      tree =
+          MergeUtil.mergeWithConflicts(
+              ctx.getRevWalk(),
+              ctx.getInserter(),
+              dc,
+              "PATCH SET",
+              original,
+              "BASE",
+              ctx.getRevWalk().parseCommit(base),
+              mergeResults);
     }
 
     CommitBuilder cb = new CommitBuilder();
-    cb.setTreeId(merger.getResultTreeId());
+    cb.setTreeId(tree);
     cb.setParentId(base);
     cb.setAuthor(original.getAuthorIdent());
     cb.setMessage(commitMessage);
@@ -290,6 +379,8 @@
     }
     ObjectId objectId = ctx.getInserter().insert(cb);
     ctx.getInserter().flush();
-    return ctx.getRevWalk().parseCommit(objectId);
+    CodeReviewCommit commit = ((CodeReviewRevWalk) ctx.getRevWalk()).parseCommit(objectId);
+    commit.setFilesWithGitConflicts(filesWithGitConflicts);
+    return commit;
   }
 }
diff --git a/java/com/google/gerrit/server/git/MergeUtil.java b/java/com/google/gerrit/server/git/MergeUtil.java
index 8666f26..fd1a017 100644
--- a/java/com/google/gerrit/server/git/MergeUtil.java
+++ b/java/com/google/gerrit/server/git/MergeUtil.java
@@ -488,6 +488,10 @@
   }
 
   public static String createConflictMessage(List<String> conflicts) {
+    if (conflicts.isEmpty()) {
+      return "";
+    }
+
     StringBuilder sb = new StringBuilder("merge conflict(s):");
     for (String c : conflicts) {
       sb.append('\n').append(c);
diff --git a/java/com/google/gerrit/server/restapi/change/CherryPickChange.java b/java/com/google/gerrit/server/restapi/change/CherryPickChange.java
index 5753874..a3e0cf0 100644
--- a/java/com/google/gerrit/server/restapi/change/CherryPickChange.java
+++ b/java/com/google/gerrit/server/restapi/change/CherryPickChange.java
@@ -334,7 +334,7 @@
                 input.allowEmpty,
                 input.allowConflicts);
       } catch (MergeIdenticalTreeException | MergeConflictException e) {
-        throw new IntegrationConflictException("Cherry pick failed: " + e.getMessage());
+        throw new IntegrationConflictException("Cherry pick failed: " + e.getMessage(), e);
       }
 
       try (BatchUpdate bu = batchUpdateFactory.create(project, identifiedUser, timestamp)) {
diff --git a/java/com/google/gerrit/server/restapi/change/Rebase.java b/java/com/google/gerrit/server/restapi/change/Rebase.java
index 75ba4c1..cfdf04d 100644
--- a/java/com/google/gerrit/server/restapi/change/Rebase.java
+++ b/java/com/google/gerrit/server/restapi/change/Rebase.java
@@ -42,6 +42,7 @@
 import com.google.gerrit.server.change.RebaseUtil;
 import com.google.gerrit.server.change.RebaseUtil.Base;
 import com.google.gerrit.server.change.RevisionResource;
+import com.google.gerrit.server.git.CodeReviewCommit;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.permissions.ChangePermission;
 import com.google.gerrit.server.permissions.PermissionBackend;
@@ -115,7 +116,7 @@
     try (Repository repo = repoManager.openRepository(change.getProject());
         ObjectInserter oi = repo.newObjectInserter();
         ObjectReader reader = oi.newReader();
-        RevWalk rw = new RevWalk(reader);
+        RevWalk rw = CodeReviewCommit.newRevWalk(reader);
         BatchUpdate bu =
             updateFactory.create(change.getProject(), rsrc.getUser(), TimeUtil.nowTs())) {
       if (!change.isNew()) {
@@ -124,18 +125,23 @@
         throw new ResourceConflictException(
             "cannot rebase merge commits or commit with no ancestor");
       }
-      // TODO(dborowitz): Why no notification? This seems wrong; dig up blame.
-      bu.setNotify(NotifyResolver.Result.none());
-      bu.setRepository(repo, rw, oi);
-      bu.addOp(
-          change.getId(),
+      RebaseChangeOp rebaseOp =
           rebaseFactory
               .create(rsrc.getNotes(), rsrc.getPatchSet(), findBaseRev(repo, rw, rsrc, input))
               .setForceContentMerge(true)
-              .setFireRevisionCreated(true));
+              .setAllowConflicts(input.allowConflicts)
+              .setFireRevisionCreated(true);
+      // TODO(dborowitz): Why no notification? This seems wrong; dig up blame.
+      bu.setNotify(NotifyResolver.Result.none());
+      bu.setRepository(repo, rw, oi);
+      bu.addOp(change.getId(), rebaseOp);
       bu.execute();
+
+      ChangeInfo changeInfo = json.create(OPTIONS).format(change.getProject(), change.getId());
+      changeInfo.containsGitConflicts =
+          !rebaseOp.getRebasedCommit().getFilesWithGitConflicts().isEmpty() ? true : null;
+      return Response.ok(changeInfo);
     }
-    return Response.ok(json.create(OPTIONS).format(change.getProject(), change.getId()));
   }
 
   private ObjectId findBaseRev(
diff --git a/java/com/google/gerrit/server/restapi/project/ConfigInfoImpl.java b/java/com/google/gerrit/server/restapi/project/ConfigInfoCreator.java
similarity index 77%
rename from java/com/google/gerrit/server/restapi/project/ConfigInfoImpl.java
rename to java/com/google/gerrit/server/restapi/project/ConfigInfoCreator.java
index 783b39b..904a16f 100644
--- a/java/com/google/gerrit/server/restapi/project/ConfigInfoImpl.java
+++ b/java/com/google/gerrit/server/restapi/project/ConfigInfoCreator.java
@@ -21,6 +21,10 @@
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.extensions.api.projects.CommentLinkInfo;
 import com.google.gerrit.extensions.api.projects.ConfigInfo;
+import com.google.gerrit.extensions.api.projects.ConfigInfo.ConfigParameterInfo;
+import com.google.gerrit.extensions.api.projects.ConfigInfo.InheritedBooleanInfo;
+import com.google.gerrit.extensions.api.projects.ConfigInfo.MaxObjectSizeLimitInfo;
+import com.google.gerrit.extensions.api.projects.ConfigInfo.SubmitTypeInfo;
 import com.google.gerrit.extensions.api.projects.ProjectConfigEntryType;
 import com.google.gerrit.extensions.common.ActionInfo;
 import com.google.gerrit.extensions.registration.DynamicMap;
@@ -42,9 +46,12 @@
 import java.util.Map;
 import java.util.TreeMap;
 
-public class ConfigInfoImpl extends ConfigInfo {
+public class ConfigInfoCreator {
+  /** do not instantiate this class. */
+  private ConfigInfoCreator() {}
+
   @SuppressWarnings("deprecation")
-  public ConfigInfoImpl(
+  public static ConfigInfo constructInfo(
       boolean serverEnableSignedPush,
       ProjectState projectState,
       CurrentUser user,
@@ -53,8 +60,9 @@
       AllProjectsName allProjects,
       UiActions uiActions,
       DynamicMap<RestView<ProjectResource>> views) {
+    ConfigInfo configInfo = new ConfigInfo();
     Project p = projectState.getProject();
-    this.description = Strings.emptyToNull(p.getDescription());
+    configInfo.description = Strings.emptyToNull(p.getDescription());
 
     ProjectState parentState = Iterables.getFirst(projectState.parents(), null);
     for (BooleanProjectConfig cfg : BooleanProjectConfig.values()) {
@@ -63,48 +71,51 @@
       if (parentState != null) {
         info.inheritedValue = parentState.is(cfg);
       }
-      BooleanProjectConfigTransformations.set(cfg, this, info);
+      BooleanProjectConfigTransformations.set(cfg, configInfo, info);
     }
 
     if (!serverEnableSignedPush) {
-      this.enableSignedPush = null;
-      this.requireSignedPush = null;
+      configInfo.enableSignedPush = null;
+      configInfo.requireSignedPush = null;
     }
 
-    this.maxObjectSizeLimit = getMaxObjectSizeLimit(projectState, p);
+    configInfo.maxObjectSizeLimit = getMaxObjectSizeLimit(projectState, p);
 
-    this.defaultSubmitType = new SubmitTypeInfo();
-    this.defaultSubmitType.value = projectState.getSubmitType();
-    this.defaultSubmitType.configuredValue =
+    configInfo.defaultSubmitType = new SubmitTypeInfo();
+    configInfo.defaultSubmitType.value = projectState.getSubmitType();
+    configInfo.defaultSubmitType.configuredValue =
         MoreObjects.firstNonNull(
             projectState.getConfig().getProject().getSubmitType(), Project.DEFAULT_SUBMIT_TYPE);
     ProjectState parent =
         projectState.isAllProjects() ? projectState : projectState.parents().get(0);
-    this.defaultSubmitType.inheritedValue = parent.getSubmitType();
+    configInfo.defaultSubmitType.inheritedValue = parent.getSubmitType();
 
-    this.submitType = this.defaultSubmitType.value;
+    configInfo.submitType = configInfo.defaultSubmitType.value;
 
-    this.state =
+    configInfo.state =
         p.getState() != com.google.gerrit.extensions.client.ProjectState.ACTIVE
             ? p.getState()
             : null;
 
-    this.commentlinks = new LinkedHashMap<>();
+    configInfo.commentlinks = new LinkedHashMap<>();
     for (CommentLinkInfo cl : projectState.getCommentLinks()) {
-      this.commentlinks.put(cl.name, cl);
+      configInfo.commentlinks.put(cl.name, cl);
     }
 
-    pluginConfig = getPluginConfig(projectState, pluginConfigEntries, cfgFactory, allProjects);
+    configInfo.pluginConfig =
+        getPluginConfig(projectState, pluginConfigEntries, cfgFactory, allProjects);
 
-    actions = new TreeMap<>();
+    configInfo.actions = new TreeMap<>();
     for (UiAction.Description d : uiActions.from(views, new ProjectResource(projectState, user))) {
-      actions.put(d.getId(), new ActionInfo(d));
+      configInfo.actions.put(d.getId(), new ActionInfo(d));
     }
 
-    this.extensionPanelNames = projectState.getConfig().getExtensionPanelSections();
+    configInfo.extensionPanelNames = projectState.getConfig().getExtensionPanelSections();
+    return configInfo;
   }
 
-  private MaxObjectSizeLimitInfo getMaxObjectSizeLimit(ProjectState projectState, Project p) {
+  private static MaxObjectSizeLimitInfo getMaxObjectSizeLimit(
+      ProjectState projectState, Project p) {
     MaxObjectSizeLimitInfo info = new MaxObjectSizeLimitInfo();
     EffectiveMaxObjectSizeLimit limit = projectState.getEffectiveMaxObjectSizeLimit();
     long value = limit.value;
@@ -114,7 +125,7 @@
     return info;
   }
 
-  private Map<String, Map<String, ConfigParameterInfo>> getPluginConfig(
+  private static Map<String, Map<String, ConfigParameterInfo>> getPluginConfig(
       ProjectState project,
       DynamicMap<ProjectConfigEntry> pluginConfigEntries,
       PluginConfigFactory cfgFactory,
@@ -162,7 +173,7 @@
     return !pluginConfig.isEmpty() ? pluginConfig : null;
   }
 
-  private String getInheritedValue(
+  private static String getInheritedValue(
       ProjectState project, PluginConfigFactory cfgFactory, Extension<ProjectConfigEntry> e) {
     ProjectConfigEntry configEntry = e.getProvider().get();
     ProjectState parent = Iterables.getFirst(project.parents(), null);
diff --git a/java/com/google/gerrit/server/restapi/project/GetConfig.java b/java/com/google/gerrit/server/restapi/project/GetConfig.java
index ad66587..8ffd5ec 100644
--- a/java/com/google/gerrit/server/restapi/project/GetConfig.java
+++ b/java/com/google/gerrit/server/restapi/project/GetConfig.java
@@ -67,7 +67,7 @@
             .project(resource.getNameKey())
             .test(ProjectPermission.READ_CONFIG);
     return Response.ok(
-        new ConfigInfoImpl(
+        ConfigInfoCreator.constructInfo(
             serverEnableSignedPush,
             resource.getProjectState(),
             resource.getUser(),
diff --git a/java/com/google/gerrit/server/restapi/project/PutConfig.java b/java/com/google/gerrit/server/restapi/project/PutConfig.java
index 55ea312..afa08cd 100644
--- a/java/com/google/gerrit/server/restapi/project/PutConfig.java
+++ b/java/com/google/gerrit/server/restapi/project/PutConfig.java
@@ -176,7 +176,7 @@
       }
 
       ProjectState state = projectStateFactory.create(projectConfigFactory.read(md).getCacheable());
-      return new ConfigInfoImpl(
+      return ConfigInfoCreator.constructInfo(
           serverEnableSignedPush,
           state,
           user.get(),
diff --git a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
index 4015ccb..ecfdd8b 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
@@ -47,6 +47,7 @@
 import static com.google.gerrit.extensions.client.ReviewerState.CC;
 import static com.google.gerrit.extensions.client.ReviewerState.REMOVED;
 import static com.google.gerrit.extensions.client.ReviewerState.REVIEWER;
+import static com.google.gerrit.git.ObjectIds.abbreviateName;
 import static com.google.gerrit.server.StarredChangesUtil.DEFAULT_LABEL;
 import static com.google.gerrit.server.group.SystemGroupBackend.ANONYMOUS_USERS;
 import static com.google.gerrit.server.group.SystemGroupBackend.CHANGE_OWNER;
@@ -142,8 +143,10 @@
 import com.google.gerrit.extensions.common.LabelInfo;
 import com.google.gerrit.extensions.common.RevisionInfo;
 import com.google.gerrit.extensions.common.TrackingIdInfo;
+import com.google.gerrit.extensions.events.WorkInProgressStateChangedListener;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.BinaryResult;
 import com.google.gerrit.extensions.restapi.MethodNotAllowedException;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
@@ -178,6 +181,7 @@
 import com.google.inject.AbstractModule;
 import com.google.inject.Inject;
 import com.google.inject.name.Named;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.ArrayList;
@@ -1340,9 +1344,102 @@
             "If09d8782c1e59dd0b33de2b1ec3595d69cc10ad5");
     PushOneCommit.Result r2 = push.to("refs/for/master");
     r2.assertOkStatus();
-    assertThrows(
-        ResourceConflictException.class,
-        () -> gApi.changes().id(r2.getChangeId()).revision(r2.getCommit().name()).rebase());
+    ResourceConflictException exception =
+        assertThrows(
+            ResourceConflictException.class,
+            () -> gApi.changes().id(r2.getChangeId()).revision(r2.getCommit().name()).rebase());
+    assertThat(exception)
+        .hasMessageThat()
+        .isEqualTo(
+            String.format(
+                "The change could not be rebased due to a conflict during merge.\n\n"
+                    + "merge conflict(s):\n%s",
+                PushOneCommit.FILE_NAME));
+  }
+
+  @Test
+  public void rebaseConflict_conflictsAllowed() throws Exception {
+    String patchSetSubject = "patch set change";
+    String patchSetContent = "patch set content";
+    String baseSubject = "base change";
+    String baseContent = "base content";
+
+    PushOneCommit.Result r1 = createChange(baseSubject, PushOneCommit.FILE_NAME, baseContent);
+    gApi.changes()
+        .id(r1.getChangeId())
+        .revision(r1.getCommit().name())
+        .review(ReviewInput.approve());
+    gApi.changes().id(r1.getChangeId()).revision(r1.getCommit().name()).submit();
+
+    testRepo.reset("HEAD~1");
+    PushOneCommit push =
+        pushFactory.create(
+            admin.newIdent(), testRepo, patchSetSubject, PushOneCommit.FILE_NAME, patchSetContent);
+    PushOneCommit.Result r2 = push.to("refs/for/master");
+    r2.assertOkStatus();
+
+    String changeId = r2.getChangeId();
+    RevCommit patchSet = r2.getCommit();
+    RevCommit base = r1.getCommit();
+
+    TestWorkInProgressStateChangedListener wipStateChangedListener =
+        new TestWorkInProgressStateChangedListener();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(wipStateChangedListener)) {
+      RebaseInput rebaseInput = new RebaseInput();
+      rebaseInput.allowConflicts = true;
+      ChangeInfo changeInfo =
+          gApi.changes().id(changeId).revision(patchSet.name()).rebaseAsInfo(rebaseInput);
+      assertThat(changeInfo.containsGitConflicts).isTrue();
+      assertThat(changeInfo.workInProgress).isTrue();
+    }
+    assertThat(wipStateChangedListener.invoked).isTrue();
+    assertThat(wipStateChangedListener.wip).isTrue();
+
+    // To get the revisions, we must retrieve the change with more change options.
+    ChangeInfo changeInfo =
+        gApi.changes().id(changeId).get(ALL_REVISIONS, CURRENT_COMMIT, CURRENT_REVISION);
+    assertThat(changeInfo.revisions).hasSize(2);
+    assertThat(changeInfo.revisions.get(changeInfo.currentRevision).commit.parents.get(0).commit)
+        .isEqualTo(base.name());
+
+    // Verify that the file content in the created patch set is correct.
+    // We expect that it has conflict markers to indicate the conflict.
+    BinaryResult bin =
+        gApi.changes().id(changeId).current().file(PushOneCommit.FILE_NAME).content();
+    ByteArrayOutputStream os = new ByteArrayOutputStream();
+    bin.writeTo(os);
+    String fileContent = new String(os.toByteArray(), UTF_8);
+    String patchSetSha1 = abbreviateName(patchSet, 6);
+    String baseSha1 = abbreviateName(base, 6);
+    assertThat(fileContent)
+        .isEqualTo(
+            "<<<<<<< PATCH SET ("
+                + patchSetSha1
+                + " "
+                + patchSetSubject
+                + ")\n"
+                + patchSetContent
+                + "\n"
+                + "=======\n"
+                + baseContent
+                + "\n"
+                + ">>>>>>> BASE      ("
+                + baseSha1
+                + " "
+                + baseSubject
+                + ")\n");
+
+    // Verify the message that has been posted on the change.
+    List<ChangeMessageInfo> messages = gApi.changes().id(changeId).messages();
+    assertThat(messages).hasSize(2);
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            "Patch Set 2: Patch Set 1 was rebased\n\n"
+                + "The following files contain Git conflicts:\n"
+                + "* "
+                + PushOneCommit.FILE_NAME
+                + "\n");
   }
 
   @Test
@@ -4354,4 +4451,17 @@
   private interface AddReviewerCaller {
     void call(String changeId, String reviewer) throws RestApiException;
   }
+
+  private static class TestWorkInProgressStateChangedListener
+      implements WorkInProgressStateChangedListener {
+    boolean invoked;
+    Boolean wip;
+
+    @Override
+    public void onWorkInProgressStateChanged(Event event) {
+      this.invoked = true;
+      this.wip =
+          event.getChange().workInProgress != null ? event.getChange().workInProgress : false;
+    }
+  }
 }
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmit.java b/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmit.java
index 2891d4b..cbfbab6 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmit.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmit.java
@@ -228,7 +228,9 @@
                   "Cannot rebase "
                       + change2hash
                       + ": The change could "
-                      + "not be rebased due to a conflict during merge.");
+                      + "not be rebased due to a conflict during merge.\n\n"
+                      + "merge conflict(s):\n"
+                      + "a.txt");
           break;
         case MERGE_ALWAYS:
         case MERGE_IF_NECESSARY:
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmitByRebase.java b/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmitByRebase.java
index 5eb19df..81c098f 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmitByRebase.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmitByRebase.java
@@ -236,7 +236,9 @@
         change2.getChangeId(),
         "Cannot rebase "
             + change2.getCommit().name()
-            + ": The change could not be rebased due to a conflict during merge.");
+            + ": The change could not be rebased due to a conflict during merge.\n\n"
+            + "merge conflict(s):\n"
+            + "a.txt");
     RevCommit head = projectOperations.project(project).getHead("master");
     assertThat(head).isEqualTo(headAfterFirstSubmit);
     assertCurrentRevision(change2.getChangeId(), 1, change2.getCommit());
@@ -363,7 +365,9 @@
         "Cannot rebase "
             + change2.getCommit().getName()
             + ": "
-            + "The change could not be rebased due to a conflict during merge.");
+            + "The change could not be rebased due to a conflict during merge.\n\n"
+            + "merge conflict(s):\n"
+            + "fileName 2");
     assertThat(projectOperations.project(project).getHead("master")).isEqualTo(headAfterChange1);
   }
 
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.ts b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.ts
index 9574c1d..601ea80 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.ts
@@ -716,19 +716,10 @@
       }
 
       if (lineNumberEl) {
-        const ANNOTATE_MAX_LINE_LENGTH = 1000;
-        // For performance reason, we skip annotating long lines.
-        if (line.text.length < ANNOTATE_MAX_LINE_LENGTH) {
-          for (const layer of this.layers) {
-            if (typeof layer.annotate === 'function') {
-              layer.annotate(contentText, lineNumberEl, line);
-            }
+        for (const layer of this.layers) {
+          if (typeof layer.annotate === 'function') {
+            layer.annotate(contentText, lineNumberEl, line);
           }
-        } else {
-          const msg =
-            `A line is longer than ${ANNOTATE_MAX_LINE_LENGTH}.` +
-            ' Line annotation was skipped.';
-          console.warn(msg);
         }
       } else {
         console.error('The lineNumberEl is null, skipping layer annotations.');