diff --git a/java/com/google/gerrit/extensions/validators/CommentValidationContext.java b/java/com/google/gerrit/extensions/validators/CommentValidationContext.java
new file mode 100644
index 0000000..1cb00e3
--- /dev/null
+++ b/java/com/google/gerrit/extensions/validators/CommentValidationContext.java
@@ -0,0 +1,49 @@
+// Copyright (C) 2020 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.extensions.validators;
+
+import com.google.auto.value.AutoValue;
+
+/**
+ * Holds a comment validators context in order to pass it to a validation plugin.
+ *
+ * <p>This is used to provided additional context around that comment that can be used by the
+ * validator to determine what validations should be run. For example, a comment validator may only
+ * want to validate a comment if it's on a change in the project foo.
+ *
+ * @see CommentValidator
+ */
+@AutoValue
+public abstract class CommentValidationContext {
+
+  /** Returns the change id the comment is being added to. */
+  public abstract int getChangeId();
+
+  /** Returns the project the comment is being added to. */
+  public abstract String getProject();
+
+  public static Builder builder() {
+    return new AutoValue_CommentValidationContext.Builder();
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder {
+    public abstract Builder changeId(int value);
+
+    public abstract Builder project(String value);
+
+    public abstract CommentValidationContext build();
+  }
+}
diff --git a/java/com/google/gerrit/extensions/validators/CommentValidator.java b/java/com/google/gerrit/extensions/validators/CommentValidator.java
index cfefdef..ba73e46 100644
--- a/java/com/google/gerrit/extensions/validators/CommentValidator.java
+++ b/java/com/google/gerrit/extensions/validators/CommentValidator.java
@@ -30,5 +30,5 @@
    * @return An empty list if all comments are valid, or else a list of validation failures.
    */
   ImmutableList<CommentValidationFailure> validateComments(
-      ImmutableList<CommentForValidation> comments);
+      CommentValidationContext ctx, ImmutableList<CommentForValidation> comments);
 }
diff --git a/java/com/google/gerrit/git/RefUpdateUtil.java b/java/com/google/gerrit/git/RefUpdateUtil.java
index fa7b98f..bd88962 100644
--- a/java/com/google/gerrit/git/RefUpdateUtil.java
+++ b/java/com/google/gerrit/git/RefUpdateUtil.java
@@ -150,6 +150,7 @@
   public static void deleteChecked(Repository repo, String refName) throws IOException {
     RefUpdate ru = repo.updateRef(refName);
     ru.setForceUpdate(true);
+    ru.setCheckConflicting(false);
     switch (ru.delete()) {
       case FORCED:
         // Ref was deleted.
diff --git a/java/com/google/gerrit/pgm/init/InitModule.java b/java/com/google/gerrit/pgm/init/InitModule.java
index f2fc001..b658675 100644
--- a/java/com/google/gerrit/pgm/init/InitModule.java
+++ b/java/com/google/gerrit/pgm/init/InitModule.java
@@ -34,8 +34,6 @@
   @Override
   protected void configure() {
     bind(SitePaths.class);
-    bind(Libraries.class);
-    bind(LibraryDownloader.class);
     factory(Section.Factory.class);
     factory(VersionedAuthorizedKeysOnInit.Factory.class);
 
diff --git a/java/com/google/gerrit/pgm/init/Libraries.java b/java/com/google/gerrit/pgm/init/Libraries.java
deleted file mode 100644
index c599e99..0000000
--- a/java/com/google/gerrit/pgm/init/Libraries.java
+++ /dev/null
@@ -1,141 +0,0 @@
-// Copyright (C) 2009 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.pgm.init;
-
-import static java.nio.charset.StandardCharsets.UTF_8;
-
-import com.google.gerrit.pgm.init.api.LibraryDownload;
-import com.google.inject.Inject;
-import com.google.inject.Provider;
-import com.google.inject.Singleton;
-import java.io.FileNotFoundException;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.InputStreamReader;
-import java.io.Reader;
-import java.lang.reflect.Field;
-import java.lang.reflect.Modifier;
-import java.util.List;
-import org.eclipse.jgit.errors.ConfigInvalidException;
-import org.eclipse.jgit.lib.Config;
-
-/** Standard {@link LibraryDownloader} instances derived from configuration. */
-@Singleton
-class Libraries {
-  private static final String RESOURCE_FILE = "com/google/gerrit/pgm/init/libraries.config";
-
-  private final Provider<LibraryDownloader> downloadProvider;
-  private final List<String> skippedDownloads;
-  private final boolean skipAllDownloads;
-
-  /* final */ LibraryDownloader db2Driver;
-  /* final */ LibraryDownloader db2DriverLicense;
-  /* final */ LibraryDownloader hanaDriver;
-  /* final */ LibraryDownloader mariadbDriver;
-  /* final */ LibraryDownloader mysqlDriver;
-  /* final */ LibraryDownloader oracleDriver;
-
-  @Inject
-  Libraries(
-      final Provider<LibraryDownloader> downloadProvider,
-      @LibraryDownload List<String> skippedDownloads,
-      @LibraryDownload Boolean skipAllDownloads) {
-    this.downloadProvider = downloadProvider;
-    this.skippedDownloads = skippedDownloads;
-    this.skipAllDownloads = skipAllDownloads;
-    init();
-  }
-
-  private void init() {
-    final Config cfg = new Config();
-    try {
-      cfg.fromText(read(RESOURCE_FILE));
-    } catch (IOException | ConfigInvalidException e) {
-      throw new RuntimeException(e.getMessage(), e);
-    }
-
-    for (Field f : Libraries.class.getDeclaredFields()) {
-      if ((f.getModifiers() & Modifier.STATIC) == 0 && f.getType() == LibraryDownloader.class) {
-        try {
-          f.set(this, downloadProvider.get());
-        } catch (IllegalArgumentException | IllegalAccessException e) {
-          throw new IllegalStateException("Cannot initialize " + f.getName());
-        }
-      }
-    }
-
-    for (Field f : Libraries.class.getDeclaredFields()) {
-      if ((f.getModifiers() & Modifier.STATIC) == 0 && f.getType() == LibraryDownloader.class) {
-        try {
-          init(f, cfg);
-        } catch (IllegalArgumentException
-            | IllegalAccessException
-            | NoSuchFieldException
-            | SecurityException e) {
-          throw new IllegalStateException("Cannot configure " + f.getName());
-        }
-      }
-    }
-  }
-
-  private void init(Field field, Config cfg)
-      throws IllegalArgumentException, IllegalAccessException, NoSuchFieldException,
-          SecurityException {
-    String n = field.getName();
-    LibraryDownloader dl = (LibraryDownloader) field.get(this);
-    dl.setName(get(cfg, n, "name"));
-    dl.setJarUrl(get(cfg, n, "url"));
-    dl.setSHA1(getOptional(cfg, n, "sha1"));
-    dl.setRemove(get(cfg, n, "remove"));
-    for (String d : cfg.getStringList("library", n, "needs")) {
-      dl.addNeeds((LibraryDownloader) getClass().getDeclaredField(d).get(this));
-    }
-    dl.setSkipDownload(skipAllDownloads || skippedDownloads.contains(n));
-  }
-
-  private static String getOptional(Config cfg, String name, String key) {
-    return doGet(cfg, name, key, false);
-  }
-
-  private static String get(Config cfg, String name, String key) {
-    return doGet(cfg, name, key, true);
-  }
-
-  private static String doGet(Config cfg, String name, String key, boolean required) {
-    String val = cfg.getString("library", name, key);
-    if ((val == null || val.isEmpty()) && required) {
-      throw new IllegalStateException(
-          "Variable library." + name + "." + key + " is required within " + RESOURCE_FILE);
-    }
-    return val;
-  }
-
-  private static String read(String p) throws IOException {
-    try (InputStream in = Libraries.class.getClassLoader().getResourceAsStream(p)) {
-      if (in == null) {
-        throw new FileNotFoundException("Cannot load resource " + p);
-      }
-      try (Reader r = new InputStreamReader(in, UTF_8)) {
-        final StringBuilder buf = new StringBuilder();
-        final char[] tmp = new char[512];
-        int n;
-        while (0 < (n = r.read(tmp))) {
-          buf.append(tmp, 0, n);
-        }
-        return buf.toString();
-      }
-    }
-  }
-}
diff --git a/java/com/google/gerrit/pgm/init/LibraryDownloader.java b/java/com/google/gerrit/pgm/init/LibraryDownloader.java
deleted file mode 100644
index 0b31ee2..0000000
--- a/java/com/google/gerrit/pgm/init/LibraryDownloader.java
+++ /dev/null
@@ -1,316 +0,0 @@
-// Copyright (C) 2009 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.pgm.init;
-
-import com.google.common.hash.Funnels;
-import com.google.common.hash.Hasher;
-import com.google.common.hash.Hashing;
-import com.google.common.io.ByteStreams;
-import com.google.gerrit.common.Die;
-import com.google.gerrit.common.IoUtil;
-import com.google.gerrit.pgm.init.api.ConsoleUI;
-import com.google.gerrit.server.config.SitePaths;
-import com.google.inject.Inject;
-import java.io.FileNotFoundException;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.OutputStream;
-import java.net.HttpURLConnection;
-import java.net.Proxy;
-import java.net.ProxySelector;
-import java.net.URISyntaxException;
-import java.net.URL;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.Paths;
-import java.util.ArrayList;
-import java.util.List;
-import org.eclipse.jgit.util.HttpSupport;
-
-/** Get optional or required 3rd party library files into $site_path/lib. */
-class LibraryDownloader {
-  private final ConsoleUI ui;
-  private final Path lib_dir;
-  private final StaleLibraryRemover remover;
-
-  private boolean required;
-  private String name;
-  private String jarUrl;
-  private String sha1;
-  private String remove;
-  private List<LibraryDownloader> needs;
-  private LibraryDownloader neededBy;
-  private Path dst;
-  private boolean download; // download or copy
-  private boolean exists;
-  private boolean skipDownload;
-
-  @Inject
-  LibraryDownloader(ConsoleUI ui, SitePaths site, StaleLibraryRemover remover) {
-    this.ui = ui;
-    this.lib_dir = site.lib_dir;
-    this.remover = remover;
-    this.needs = new ArrayList<>(2);
-  }
-
-  void setName(String name) {
-    this.name = name;
-  }
-
-  void setJarUrl(String url) {
-    this.jarUrl = url;
-    download = jarUrl.startsWith("http");
-  }
-
-  void setSHA1(String sha1) {
-    this.sha1 = sha1;
-  }
-
-  void setRemove(String remove) {
-    this.remove = remove;
-  }
-
-  void addNeeds(LibraryDownloader lib) {
-    needs.add(lib);
-  }
-
-  void setSkipDownload(boolean skipDownload) {
-    this.skipDownload = skipDownload;
-  }
-
-  void downloadRequired() {
-    setRequired(true);
-    download();
-  }
-
-  void downloadOptional() {
-    required = false;
-    download();
-  }
-
-  private void setRequired(boolean r) {
-    required = r;
-    for (LibraryDownloader d : needs) {
-      d.setRequired(r);
-    }
-  }
-
-  private void download() {
-    if (skipDownload) {
-      return;
-    }
-
-    if (jarUrl == null || !jarUrl.contains("/")) {
-      throw new IllegalStateException("Invalid JarUrl for " + name);
-    }
-
-    final String jarName = jarUrl.substring(jarUrl.lastIndexOf('/') + 1);
-    if (jarName.contains("/") || jarName.contains("\\")) {
-      throw new IllegalStateException("Invalid JarUrl: " + jarUrl);
-    }
-
-    if (name == null) {
-      name = jarName;
-    }
-
-    dst = lib_dir.resolve(jarName);
-    if (Files.exists(dst)) {
-      exists = true;
-    } else if (shouldGet()) {
-      doGet();
-    }
-
-    if (exists) {
-      for (LibraryDownloader d : needs) {
-        d.neededBy = this;
-        d.downloadRequired();
-      }
-    }
-  }
-
-  private boolean shouldGet() {
-    if (ui.isBatch()) {
-      return required;
-    }
-    final StringBuilder msg = new StringBuilder();
-    msg.append("\n");
-    msg.append("Gerrit Code Review is not shipped with %s\n");
-    if (neededBy != null) {
-      msg.append(String.format("** This library is required by %s. **\n", neededBy.name));
-    } else if (required) {
-      msg.append("**  This library is required for your configuration. **\n");
-    } else {
-      msg.append("  If available, Gerrit can take advantage of features\n");
-      msg.append("  in the library, but will also function without it.\n");
-    }
-    msg.append(String.format("%s and install it now", download ? "Download" : "Copy"));
-    return ui.yesno(true, msg.toString(), name);
-  }
-
-  private void doGet() {
-    if (!Files.exists(lib_dir)) {
-      try {
-        Files.createDirectories(lib_dir);
-      } catch (IOException e) {
-        throw new Die("Cannot create " + lib_dir, e);
-      }
-    }
-
-    try {
-      remover.remove(remove);
-      if (download) {
-        doGetByHttp();
-      } else {
-        doGetByLocalCopy();
-      }
-      verifyFileChecksum();
-    } catch (IOException err) {
-      try {
-        Files.delete(dst);
-      } catch (IOException e) {
-        // Delete failed; leave alone.
-      }
-
-      if (ui.isBatch()) {
-        throw new Die("error: Cannot get " + jarUrl, err);
-      }
-
-      System.err.println();
-      System.err.println();
-      System.err.println("error: " + err.getMessage());
-      System.err.println("Please download:");
-      System.err.println();
-      System.err.println("  " + jarUrl);
-      System.err.println();
-      System.err.println("and save as:");
-      System.err.println();
-      System.err.println("  " + dst.toAbsolutePath());
-      System.err.println();
-      System.err.flush();
-
-      ui.waitForUser();
-
-      if (Files.exists(dst)) {
-        verifyFileChecksum();
-
-      } else if (!ui.yesno(!required, "Continue without this library")) {
-        throw new Die("aborted by user");
-      }
-    }
-
-    if (Files.exists(dst)) {
-      exists = true;
-      IoUtil.loadJARs(dst);
-    }
-  }
-
-  private void doGetByLocalCopy() throws IOException {
-    System.err.print("Copying " + jarUrl + " ...");
-    Path p = url2file(jarUrl);
-    if (!Files.exists(p)) {
-      StringBuilder msg =
-          new StringBuilder()
-              .append("\n")
-              .append("Can not find the %s at this location: %s\n")
-              .append("Please provide alternative URL");
-      p = url2file(ui.readString(null, msg.toString(), name, jarUrl));
-    }
-    Files.copy(p, dst);
-  }
-
-  private static Path url2file(String urlString) throws IOException {
-    final URL url = new URL(urlString);
-    try {
-      return Paths.get(url.toURI());
-    } catch (URISyntaxException e) {
-      return Paths.get(url.getPath());
-    }
-  }
-
-  private void doGetByHttp() throws IOException {
-    System.err.print("Downloading " + jarUrl + " ...");
-    System.err.flush();
-    try (InputStream in = openHttpStream(jarUrl);
-        OutputStream out = Files.newOutputStream(dst)) {
-      ByteStreams.copy(in, out);
-      System.err.println(" OK");
-      System.err.flush();
-    } catch (IOException err) {
-      deleteDst();
-      System.err.println(" !! FAIL !!");
-      System.err.println(err);
-      System.err.flush();
-      throw err;
-    }
-  }
-
-  private static InputStream openHttpStream(String urlStr) throws IOException {
-    ProxySelector proxySelector = ProxySelector.getDefault();
-    URL url = new URL(urlStr);
-    Proxy proxy = HttpSupport.proxyFor(proxySelector, url);
-    HttpURLConnection c = (HttpURLConnection) url.openConnection(proxy);
-
-    switch (HttpSupport.response(c)) {
-      case HttpURLConnection.HTTP_OK:
-        return c.getInputStream();
-
-      case HttpURLConnection.HTTP_NOT_FOUND:
-        throw new FileNotFoundException(url.toString());
-
-      default:
-        throw new IOException(
-            url.toString() + ": " + HttpSupport.response(c) + " " + c.getResponseMessage());
-    }
-  }
-
-  @SuppressWarnings("deprecation") // Use Hashing.sha1 for compatibility.
-  private void verifyFileChecksum() {
-    if (sha1 == null) {
-      System.err.println();
-      System.err.flush();
-      return;
-    }
-    Hasher h = Hashing.sha1().newHasher();
-    try (InputStream in = Files.newInputStream(dst);
-        OutputStream out = Funnels.asOutputStream(h)) {
-      ByteStreams.copy(in, out);
-    } catch (IOException e) {
-      deleteDst();
-      throw new Die("cannot checksum " + dst, e);
-    }
-    if (sha1.equals(h.hash().toString())) {
-      System.err.println("Checksum " + dst.getFileName() + " OK");
-      System.err.flush();
-    } else if (ui.isBatch()) {
-      deleteDst();
-      throw new Die(dst + " SHA-1 checksum does not match");
-
-    } else if (!ui.yesno(
-        null /* force an answer */,
-        "error: SHA-1 checksum does not match\nUse %s anyway", //
-        dst.getFileName())) {
-      deleteDst();
-      throw new Die("aborted by user");
-    }
-  }
-
-  private void deleteDst() {
-    try {
-      Files.delete(dst);
-    } catch (IOException e) {
-      System.err.println(" Failed to clean up lib: " + dst);
-    }
-  }
-}
diff --git a/java/com/google/gerrit/server/PublishCommentUtil.java b/java/com/google/gerrit/server/PublishCommentUtil.java
index 09042ab..3d34d6b 100644
--- a/java/com/google/gerrit/server/PublishCommentUtil.java
+++ b/java/com/google/gerrit/server/PublishCommentUtil.java
@@ -25,6 +25,7 @@
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.exceptions.StorageException;
 import com.google.gerrit.extensions.validators.CommentForValidation;
+import com.google.gerrit.extensions.validators.CommentValidationContext;
 import com.google.gerrit.extensions.validators.CommentValidationFailure;
 import com.google.gerrit.extensions.validators.CommentValidator;
 import com.google.gerrit.server.notedb.ChangeNotes;
@@ -118,16 +119,18 @@
   /**
    * Helper to run the specified set of {@link CommentValidator}-s on the specified comments.
    *
-   * @return See {@link CommentValidator#validateComments(ImmutableList)}.
+   * @return See {@link CommentValidator#validateComments(CommentValidationContext,ImmutableList)}.
    */
   public static ImmutableList<CommentValidationFailure> findInvalidComments(
+      CommentValidationContext ctx,
       PluginSetContext<CommentValidator> commentValidators,
       ImmutableList<CommentForValidation> commentsForValidation) {
     ImmutableList.Builder<CommentValidationFailure> commentValidationFailures =
         new ImmutableList.Builder<>();
     commentValidators.runEach(
         validator ->
-            commentValidationFailures.addAll(validator.validateComments(commentsForValidation)));
+            commentValidationFailures.addAll(
+                validator.validateComments(ctx, commentsForValidation)));
     return commentValidationFailures.build();
   }
 }
diff --git a/java/com/google/gerrit/server/change/FileInfoJson.java b/java/com/google/gerrit/server/change/FileInfoJson.java
index a823975..aca4fb0 100644
--- a/java/com/google/gerrit/server/change/FileInfoJson.java
+++ b/java/com/google/gerrit/server/change/FileInfoJson.java
@@ -21,6 +21,7 @@
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.extensions.client.DiffPreferencesInfo.Whitespace;
 import com.google.gerrit.extensions.common.FileInfo;
+import com.google.gerrit.extensions.restapi.ResourceConflictException;
 import com.google.gerrit.server.patch.PatchList;
 import com.google.gerrit.server.patch.PatchListCache;
 import com.google.gerrit.server.patch.PatchListEntry;
@@ -30,6 +31,8 @@
 import com.google.inject.Singleton;
 import java.util.Map;
 import java.util.TreeMap;
+import java.util.concurrent.ExecutionException;
+import org.eclipse.jgit.errors.NoMergeBaseException;
 import org.eclipse.jgit.lib.ObjectId;
 
 @Singleton
@@ -42,31 +45,44 @@
   }
 
   public Map<String, FileInfo> toFileInfoMap(Change change, PatchSet patchSet)
-      throws PatchListNotAvailableException {
+      throws ResourceConflictException, PatchListNotAvailableException {
     return toFileInfoMap(change, patchSet.commitId(), null);
   }
 
   public Map<String, FileInfo> toFileInfoMap(
       Change change, ObjectId objectId, @Nullable PatchSet base)
-      throws PatchListNotAvailableException {
+      throws ResourceConflictException, PatchListNotAvailableException {
     ObjectId a = base != null ? base.commitId() : null;
     return toFileInfoMap(change, PatchListKey.againstCommit(a, objectId, Whitespace.IGNORE_NONE));
   }
 
   public Map<String, FileInfo> toFileInfoMap(Change change, ObjectId objectId, int parent)
-      throws PatchListNotAvailableException {
+      throws ResourceConflictException, PatchListNotAvailableException {
     return toFileInfoMap(
         change, PatchListKey.againstParentNum(parent + 1, objectId, Whitespace.IGNORE_NONE));
   }
 
   private Map<String, FileInfo> toFileInfoMap(Change change, PatchListKey key)
-      throws PatchListNotAvailableException {
+      throws ResourceConflictException, PatchListNotAvailableException {
     return toFileInfoMap(change.getProject(), key);
   }
 
   public Map<String, FileInfo> toFileInfoMap(Project.NameKey project, PatchListKey key)
-      throws PatchListNotAvailableException {
-    PatchList list = patchListCache.get(key, project);
+      throws ResourceConflictException, PatchListNotAvailableException {
+    PatchList list;
+    try {
+      list = patchListCache.get(key, project);
+    } catch (PatchListNotAvailableException e) {
+      Throwable cause = e.getCause();
+      if (cause instanceof ExecutionException) {
+        cause = cause.getCause();
+      }
+      if (cause instanceof NoMergeBaseException) {
+        throw new ResourceConflictException(
+            String.format("Cannot create auto merge commit: %s", e.getMessage()), e);
+      }
+      throw e;
+    }
 
     Map<String, FileInfo> files = new TreeMap<>();
     for (PatchListEntry e : list.getPatches()) {
diff --git a/java/com/google/gerrit/server/change/RevisionJson.java b/java/com/google/gerrit/server/change/RevisionJson.java
index fbd14c4..a4994fd 100644
--- a/java/com/google/gerrit/server/change/RevisionJson.java
+++ b/java/com/google/gerrit/server/change/RevisionJson.java
@@ -49,6 +49,7 @@
 import com.google.gerrit.extensions.registration.DynamicMap;
 import com.google.gerrit.extensions.registration.Extension;
 import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.extensions.restapi.ResourceConflictException;
 import com.google.gerrit.server.AnonymousUser;
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.GpgException;
@@ -311,9 +312,13 @@
     }
 
     if (has(ALL_FILES) || (out.isCurrent && has(CURRENT_FILES))) {
-      out.files = fileInfoJson.toFileInfoMap(c, in);
-      out.files.remove(Patch.COMMIT_MSG);
-      out.files.remove(Patch.MERGE_LIST);
+      try {
+        out.files = fileInfoJson.toFileInfoMap(c, in);
+        out.files.remove(Patch.COMMIT_MSG);
+        out.files.remove(Patch.MERGE_LIST);
+      } catch (ResourceConflictException e) {
+        logger.atWarning().withCause(e).log("creating file list failed");
+      }
     }
 
     if (out.isCurrent && has(CURRENT_ACTIONS) && userProvider.get().isIdentifiedUser()) {
diff --git a/java/com/google/gerrit/server/edit/ChangeEditModifier.java b/java/com/google/gerrit/server/edit/ChangeEditModifier.java
index c05a47d..128388d 100644
--- a/java/com/google/gerrit/server/edit/ChangeEditModifier.java
+++ b/java/com/google/gerrit/server/edit/ChangeEditModifier.java
@@ -53,6 +53,7 @@
 import java.util.List;
 import java.util.Optional;
 import java.util.TimeZone;
+import org.eclipse.jgit.dircache.InvalidPathException;
 import org.eclipse.jgit.lib.BatchRefUpdate;
 import org.eclipse.jgit.lib.CommitBuilder;
 import org.eclipse.jgit.lib.NullProgressMonitor;
@@ -250,13 +251,14 @@
    * @param filePath the path of the file whose contents should be modified
    * @param newContent the new file content
    * @throws AuthException if the user isn't authenticated or not allowed to use change edits
+   * @throws BadRequestException if the user provided bad input (e.g. invalid file paths)
    * @throws InvalidChangeOperationException if the file already had the specified content
    * @throws PermissionBackendException
    * @throws ResourceConflictException if the project state does not permit the operation
    */
   public void modifyFile(
       Repository repository, ChangeNotes notes, String filePath, RawInput newContent)
-      throws AuthException, InvalidChangeOperationException, IOException,
+      throws AuthException, BadRequestException, InvalidChangeOperationException, IOException,
           PermissionBackendException, ResourceConflictException {
     modifyTree(repository, notes, new ChangeFileContentModification(filePath, newContent));
   }
@@ -269,12 +271,13 @@
    * @param notes the {@link ChangeNotes} of the change whose change edit should be modified
    * @param file path of the file which should be deleted
    * @throws AuthException if the user isn't authenticated or not allowed to use change edits
+   * @throws BadRequestException if the user provided bad input (e.g. invalid file paths)
    * @throws InvalidChangeOperationException if the file does not exist
    * @throws PermissionBackendException
    * @throws ResourceConflictException if the project state does not permit the operation
    */
   public void deleteFile(Repository repository, ChangeNotes notes, String file)
-      throws AuthException, InvalidChangeOperationException, IOException,
+      throws AuthException, BadRequestException, InvalidChangeOperationException, IOException,
           PermissionBackendException, ResourceConflictException {
     modifyTree(repository, notes, new DeleteFileModification(file));
   }
@@ -288,6 +291,7 @@
    * @param currentFilePath the current path/name of the file
    * @param newFilePath the desired path/name of the file
    * @throws AuthException if the user isn't authenticated or not allowed to use change edits
+   * @throws BadRequestException if the user provided bad input (e.g. invalid file paths)
    * @throws InvalidChangeOperationException if the file was already renamed to the specified new
    *     name
    * @throws PermissionBackendException
@@ -295,7 +299,7 @@
    */
   public void renameFile(
       Repository repository, ChangeNotes notes, String currentFilePath, String newFilePath)
-      throws AuthException, InvalidChangeOperationException, IOException,
+      throws AuthException, BadRequestException, InvalidChangeOperationException, IOException,
           PermissionBackendException, ResourceConflictException {
     modifyTree(repository, notes, new RenameFileModification(currentFilePath, newFilePath));
   }
@@ -313,14 +317,14 @@
    * @throws PermissionBackendException
    */
   public void restoreFile(Repository repository, ChangeNotes notes, String file)
-      throws AuthException, InvalidChangeOperationException, IOException,
+      throws AuthException, BadRequestException, InvalidChangeOperationException, IOException,
           PermissionBackendException, ResourceConflictException {
     modifyTree(repository, notes, new RestoreFileModification(file));
   }
 
   private void modifyTree(
       Repository repository, ChangeNotes notes, TreeModification treeModification)
-      throws AuthException, IOException, InvalidChangeOperationException,
+      throws AuthException, BadRequestException, IOException, InvalidChangeOperationException,
           PermissionBackendException, ResourceConflictException {
     assertCanEdit(notes);
 
@@ -370,8 +374,8 @@
       ChangeNotes notes,
       PatchSet patchSet,
       List<TreeModification> treeModifications)
-      throws AuthException, IOException, InvalidChangeOperationException, MergeConflictException,
-          PermissionBackendException, ResourceConflictException {
+      throws AuthException, BadRequestException, IOException, InvalidChangeOperationException,
+          MergeConflictException, PermissionBackendException, ResourceConflictException {
     assertCanEdit(notes);
 
     Optional<ChangeEdit> optionalChangeEdit = lookupChangeEdit(notes);
@@ -486,10 +490,15 @@
 
   private static ObjectId createNewTree(
       Repository repository, RevCommit baseCommit, List<TreeModification> treeModifications)
-      throws IOException, InvalidChangeOperationException {
-    TreeCreator treeCreator = new TreeCreator(baseCommit);
-    treeCreator.addTreeModifications(treeModifications);
-    ObjectId newTreeId = treeCreator.createNewTreeAndGetId(repository);
+      throws BadRequestException, IOException, InvalidChangeOperationException {
+    ObjectId newTreeId;
+    try {
+      TreeCreator treeCreator = new TreeCreator(baseCommit);
+      treeCreator.addTreeModifications(treeModifications);
+      newTreeId = treeCreator.createNewTreeAndGetId(repository);
+    } catch (InvalidPathException e) {
+      throw new BadRequestException(e.getMessage());
+    }
 
     if (ObjectId.isEqual(newTreeId, baseCommit.getTree())) {
       throw new InvalidChangeOperationException("no changes were made");
diff --git a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
index 3d531b2..d8aa054 100644
--- a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
+++ b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
@@ -93,6 +93,7 @@
 import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
 import com.google.gerrit.extensions.validators.CommentForValidation;
 import com.google.gerrit.extensions.validators.CommentForValidation.CommentType;
+import com.google.gerrit.extensions.validators.CommentValidationContext;
 import com.google.gerrit.extensions.validators.CommentValidationFailure;
 import com.google.gerrit.extensions.validators.CommentValidator;
 import com.google.gerrit.server.ApprovalsUtil;
@@ -2014,8 +2015,13 @@
                                 : CommentType.FILE_COMMENT,
                             comment.message))
                 .collect(toImmutableList());
+        CommentValidationContext ctx =
+            CommentValidationContext.builder()
+                .changeId(change.getChangeId())
+                .project(change.getProject().get())
+                .build();
         ImmutableList<CommentValidationFailure> commentValidationFailures =
-            PublishCommentUtil.findInvalidComments(commentValidators, draftsForValidation);
+            PublishCommentUtil.findInvalidComments(ctx, commentValidators, draftsForValidation);
         magicBranch.setCommentsValid(commentValidationFailures.isEmpty());
         commentValidationFailures.forEach(
             failure ->
@@ -3337,7 +3343,8 @@
                     }
 
                     logger.atFine().log(
-                        "Auto-closing %d changes with existing patch sets and %d with new patch sets",
+                        "Auto-closing %d changes with existing patch sets and %d with new patch"
+                            + " sets",
                         existingPatchSets, newPatchSets);
                     bu.execute();
                   } catch (IOException | StorageException | PermissionBackendException e) {
diff --git a/java/com/google/gerrit/server/git/validators/CommentLimitsValidator.java b/java/com/google/gerrit/server/git/validators/CommentLimitsValidator.java
index 8237e69..3a8bcac 100644
--- a/java/com/google/gerrit/server/git/validators/CommentLimitsValidator.java
+++ b/java/com/google/gerrit/server/git/validators/CommentLimitsValidator.java
@@ -16,6 +16,7 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.gerrit.extensions.validators.CommentForValidation;
+import com.google.gerrit.extensions.validators.CommentValidationContext;
 import com.google.gerrit.extensions.validators.CommentValidationFailure;
 import com.google.gerrit.extensions.validators.CommentValidator;
 import com.google.gerrit.server.config.GerritServerConfig;
@@ -33,7 +34,7 @@
 
   @Override
   public ImmutableList<CommentValidationFailure> validateComments(
-      ImmutableList<CommentForValidation> comments) {
+      CommentValidationContext ctx, ImmutableList<CommentForValidation> comments) {
     return comments.stream()
         .filter(c -> c.getText().length() > maxCommentLength)
         .map(
diff --git a/java/com/google/gerrit/server/mail/receive/MailProcessor.java b/java/com/google/gerrit/server/mail/receive/MailProcessor.java
index 71d8c15..e79696a 100644
--- a/java/com/google/gerrit/server/mail/receive/MailProcessor.java
+++ b/java/com/google/gerrit/server/mail/receive/MailProcessor.java
@@ -34,6 +34,7 @@
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
 import com.google.gerrit.extensions.validators.CommentForValidation;
+import com.google.gerrit.extensions.validators.CommentValidationContext;
 import com.google.gerrit.extensions.validators.CommentValidationFailure;
 import com.google.gerrit.extensions.validators.CommentValidator;
 import com.google.gerrit.mail.HtmlParser;
@@ -287,8 +288,14 @@
                           MAIL_COMMENT_TYPE_TO_VALIDATION_TYPE.get(comment.getType()),
                           comment.getMessage()))
               .collect(ImmutableList.toImmutableList());
+      CommentValidationContext commentValidationCtx =
+          CommentValidationContext.builder()
+              .changeId(cd.change().getChangeId())
+              .project(cd.change().getProject().get())
+              .build();
       ImmutableList<CommentValidationFailure> commentValidationFailures =
-          PublishCommentUtil.findInvalidComments(commentValidators, parsedCommentsForValidation);
+          PublishCommentUtil.findInvalidComments(
+              commentValidationCtx, commentValidators, parsedCommentsForValidation);
       if (!commentValidationFailures.isEmpty()) {
         sendRejectionEmail(message, InboundEmailRejectionSender.Error.COMMENT_REJECTED);
         return;
diff --git a/java/com/google/gerrit/server/restapi/change/ChangeEdits.java b/java/com/google/gerrit/server/restapi/change/ChangeEdits.java
index aa36b73..cbc1b79 100644
--- a/java/com/google/gerrit/server/restapi/change/ChangeEdits.java
+++ b/java/com/google/gerrit/server/restapi/change/ChangeEdits.java
@@ -138,7 +138,8 @@
 
     @Override
     public Response<?> apply(ChangeResource rsrc, IdString id, Input in)
-        throws IOException, AuthException, ResourceConflictException, PermissionBackendException {
+        throws IOException, AuthException, BadRequestException, ResourceConflictException,
+            PermissionBackendException {
       return deleteContent.apply(rsrc, id.get());
     }
   }
@@ -184,7 +185,8 @@
 
     @Override
     public Response<EditInfo> apply(ChangeResource rsrc)
-        throws AuthException, IOException, ResourceNotFoundException, PermissionBackendException {
+        throws AuthException, IOException, ResourceNotFoundException, ResourceConflictException,
+            PermissionBackendException {
       Optional<ChangeEdit> edit = editUtil.byChange(rsrc.getNotes(), rsrc.getUser());
       if (!edit.isPresent()) {
         return Response.none();
@@ -239,7 +241,8 @@
 
     @Override
     public Response<?> apply(ChangeResource resource, Post.Input input)
-        throws AuthException, IOException, ResourceConflictException, PermissionBackendException {
+        throws AuthException, BadRequestException, IOException, ResourceConflictException,
+            PermissionBackendException {
       Project.NameKey project = resource.getProject();
       try (Repository repository = repositoryManager.openRepository(project)) {
         if (isRestoreFile(input)) {
@@ -325,12 +328,14 @@
 
     @Override
     public Response<?> apply(ChangeEditResource rsrc, Input input)
-        throws AuthException, ResourceConflictException, IOException, PermissionBackendException {
+        throws AuthException, BadRequestException, ResourceConflictException, IOException,
+            PermissionBackendException {
       return apply(rsrc.getChangeResource(), rsrc.getPath());
     }
 
     public Response<?> apply(ChangeResource rsrc, String filePath)
-        throws AuthException, IOException, ResourceConflictException, PermissionBackendException {
+        throws AuthException, BadRequestException, IOException, ResourceConflictException,
+            PermissionBackendException {
       try (Repository repository = repositoryManager.openRepository(rsrc.getProject())) {
         editModifier.deleteFile(repository, rsrc.getNotes(), filePath);
       } catch (InvalidChangeOperationException e) {
diff --git a/java/com/google/gerrit/server/restapi/change/PostReview.java b/java/com/google/gerrit/server/restapi/change/PostReview.java
index 03c2fc4..324069d 100644
--- a/java/com/google/gerrit/server/restapi/change/PostReview.java
+++ b/java/com/google/gerrit/server/restapi/change/PostReview.java
@@ -77,6 +77,7 @@
 import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
 import com.google.gerrit.extensions.restapi.Url;
 import com.google.gerrit.extensions.validators.CommentForValidation;
+import com.google.gerrit.extensions.validators.CommentValidationContext;
 import com.google.gerrit.extensions.validators.CommentValidationFailure;
 import com.google.gerrit.extensions.validators.CommentValidator;
 import com.google.gerrit.json.OutputFormat;
@@ -999,16 +1000,22 @@
         }
       }
 
+      CommentValidationContext commentValidationCtx =
+          CommentValidationContext.builder()
+              .changeId(ctx.getChange().getChangeId())
+              .project(ctx.getChange().getProject().get())
+              .build();
       switch (in.drafts) {
         case PUBLISH:
         case PUBLISH_ALL_REVISIONS:
-          validateComments(Streams.concat(drafts.values().stream(), toPublish.stream()));
+          validateComments(
+              commentValidationCtx, Streams.concat(drafts.values().stream(), toPublish.stream()));
           publishCommentUtil.publish(ctx, ctx.getUpdate(psId), drafts.values(), in.tag);
           comments.addAll(drafts.values());
           break;
         case KEEP:
         default:
-          validateComments(toPublish.stream());
+          validateComments(commentValidationCtx, toPublish.stream());
           break;
       }
       ChangeUpdate changeUpdate = ctx.getUpdate(psId);
@@ -1017,7 +1024,8 @@
       return !toPublish.isEmpty();
     }
 
-    private void validateComments(Stream<Comment> comments) throws CommentsRejectedException {
+    private void validateComments(CommentValidationContext ctx, Stream<Comment> comments)
+        throws CommentsRejectedException {
       ImmutableList<CommentForValidation> draftsForValidation =
           comments
               .map(
@@ -1029,7 +1037,7 @@
                           comment.message))
               .collect(toImmutableList());
       ImmutableList<CommentValidationFailure> draftValidationFailures =
-          PublishCommentUtil.findInvalidComments(commentValidators, draftsForValidation);
+          PublishCommentUtil.findInvalidComments(ctx, commentValidators, draftsForValidation);
       if (!draftValidationFailures.isEmpty()) {
         throw new CommentsRejectedException(draftValidationFailures);
       }
@@ -1415,8 +1423,14 @@
         buf.append(String.format("\n\n(%d comments)", comments.size()));
       }
       if (!msg.isEmpty()) {
+        CommentValidationContext commentValidationCtx =
+            CommentValidationContext.builder()
+                .changeId(ctx.getChange().getChangeId())
+                .project(ctx.getChange().getProject().get())
+                .build();
         ImmutableList<CommentValidationFailure> messageValidationFailure =
             PublishCommentUtil.findInvalidComments(
+                commentValidationCtx,
                 commentValidators,
                 ImmutableList.of(
                     CommentForValidation.create(
diff --git a/java/com/google/gerrit/server/restapi/project/FilesInCommitCollection.java b/java/com/google/gerrit/server/restapi/project/FilesInCommitCollection.java
index 0ee8279..0d5ab88 100644
--- a/java/com/google/gerrit/server/restapi/project/FilesInCommitCollection.java
+++ b/java/com/google/gerrit/server/restapi/project/FilesInCommitCollection.java
@@ -20,6 +20,7 @@
 import com.google.gerrit.extensions.registration.DynamicMap;
 import com.google.gerrit.extensions.restapi.ChildCollection;
 import com.google.gerrit.extensions.restapi.IdString;
+import com.google.gerrit.extensions.restapi.ResourceConflictException;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestReadView;
@@ -86,7 +87,7 @@
 
     @Override
     public Response<Map<String, FileInfo>> apply(CommitResource resource)
-        throws PatchListNotAvailableException {
+        throws ResourceConflictException, PatchListNotAvailableException {
       RevCommit commit = resource.getCommit();
       PatchListKey key;
 
diff --git a/javatests/com/google/gerrit/acceptance/api/change/PostReviewIT.java b/javatests/com/google/gerrit/acceptance/api/change/PostReviewIT.java
index 7156c8d..524a05e 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/PostReviewIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/PostReviewIT.java
@@ -16,6 +16,7 @@
 
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.clearInvocations;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
@@ -37,6 +38,7 @@
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.validators.CommentForValidation;
 import com.google.gerrit.extensions.validators.CommentForValidation.CommentType;
+import com.google.gerrit.extensions.validators.CommentValidationContext;
 import com.google.gerrit.extensions.validators.CommentValidator;
 import com.google.gerrit.server.restapi.change.PostReview;
 import com.google.gerrit.server.update.CommentsRejectedException;
@@ -80,14 +82,17 @@
 
   @Test
   public void validateCommentsInInput_commentOK() throws Exception {
+    PushOneCommit.Result r = createChange();
     when(mockCommentValidator.validateComments(
+            CommentValidationContext.builder()
+                .changeId(r.getChange().getId().get())
+                .project(r.getChange().project().get())
+                .build(),
             ImmutableList.of(
                 CommentForValidation.create(
                     CommentForValidation.CommentType.FILE_COMMENT, COMMENT_TEXT))))
         .thenReturn(ImmutableList.of());
 
-    PushOneCommit.Result r = createChange();
-
     ReviewInput input = new ReviewInput();
     CommentInput comment = newComment(r.getChange().currentFilePaths().get(0));
     comment.updated = new Timestamp(0);
@@ -101,14 +106,17 @@
 
   @Test
   public void validateCommentsInInput_commentRejected() throws Exception {
+    PushOneCommit.Result r = createChange();
     CommentForValidation commentForValidation =
         CommentForValidation.create(CommentType.FILE_COMMENT, COMMENT_TEXT);
     when(mockCommentValidator.validateComments(
+            CommentValidationContext.builder()
+                .changeId(r.getChange().getId().get())
+                .project(r.getChange().project().get())
+                .build(),
             ImmutableList.of(CommentForValidation.create(CommentType.FILE_COMMENT, COMMENT_TEXT))))
         .thenReturn(ImmutableList.of(commentForValidation.failValidation("Oh no!")));
 
-    PushOneCommit.Result r = createChange();
-
     ReviewInput input = new ReviewInput();
     CommentInput comment = newComment(r.getChange().currentFilePaths().get(0));
     comment.updated = new Timestamp(0);
@@ -151,14 +159,17 @@
 
   @Test
   public void validateDrafts_draftOK() throws Exception {
+    PushOneCommit.Result r = createChange();
     when(mockCommentValidator.validateComments(
+            CommentValidationContext.builder()
+                .changeId(r.getChange().getId().get())
+                .project(r.getChange().project().get())
+                .build(),
             ImmutableList.of(
                 CommentForValidation.create(
                     CommentForValidation.CommentType.INLINE_COMMENT, COMMENT_TEXT))))
         .thenReturn(ImmutableList.of());
 
-    PushOneCommit.Result r = createChange();
-
     DraftInput draft =
         testCommentHelper.newDraft(
             r.getChange().currentFilePaths().get(0), Side.REVISION, 1, COMMENT_TEXT);
@@ -174,14 +185,18 @@
 
   @Test
   public void validateDrafts_draftRejected() throws Exception {
+    PushOneCommit.Result r = createChange();
     CommentForValidation commentForValidation =
         CommentForValidation.create(CommentType.INLINE_COMMENT, COMMENT_TEXT);
     when(mockCommentValidator.validateComments(
+            CommentValidationContext.builder()
+                .changeId(r.getChange().getId().get())
+                .project(r.getChange().project().get())
+                .build(),
             ImmutableList.of(
                 CommentForValidation.create(
                     CommentForValidation.CommentType.INLINE_COMMENT, COMMENT_TEXT))))
         .thenReturn(ImmutableList.of(commentForValidation.failValidation("Oh no!")));
-    PushOneCommit.Result r = createChange();
 
     DraftInput draft =
         testCommentHelper.newDraft(
@@ -218,7 +233,8 @@
     testCommentHelper.addDraft(r.getChangeId(), r.getCommit().getName(), draftFile);
     assertThat(testCommentHelper.getPublishedComments(r.getChangeId())).isEmpty();
 
-    when(mockCommentValidator.validateComments(capture.capture())).thenReturn(ImmutableList.of());
+    when(mockCommentValidator.validateComments(any(), capture.capture()))
+        .thenReturn(ImmutableList.of());
 
     ReviewInput input = new ReviewInput();
     input.drafts = DraftHandling.PUBLISH;
@@ -236,11 +252,15 @@
 
   @Test
   public void validateCommentsInChangeMessage_messageOK() throws Exception {
+    PushOneCommit.Result r = createChange();
     when(mockCommentValidator.validateComments(
+            CommentValidationContext.builder()
+                .changeId(r.getChange().getId().get())
+                .project(r.getChange().project().get())
+                .build(),
             ImmutableList.of(
                 CommentForValidation.create(CommentType.CHANGE_MESSAGE, COMMENT_TEXT))))
         .thenReturn(ImmutableList.of());
-    PushOneCommit.Result r = createChange();
 
     ReviewInput input = new ReviewInput().message(COMMENT_TEXT);
     int numMessages = gApi.changes().id(r.getChangeId()).get().messages.size();
@@ -253,13 +273,17 @@
 
   @Test
   public void validateCommentsInChangeMessage_messageRejected() throws Exception {
+    PushOneCommit.Result r = createChange();
     CommentForValidation commentForValidation =
         CommentForValidation.create(CommentType.CHANGE_MESSAGE, COMMENT_TEXT);
     when(mockCommentValidator.validateComments(
+            CommentValidationContext.builder()
+                .changeId(r.getChange().getId().get())
+                .project(r.getChange().project().get())
+                .build(),
             ImmutableList.of(
                 CommentForValidation.create(CommentType.CHANGE_MESSAGE, COMMENT_TEXT))))
         .thenReturn(ImmutableList.of(commentForValidation.failValidation("Oh no!")));
-    PushOneCommit.Result r = createChange();
 
     ReviewInput input = new ReviewInput().message(COMMENT_TEXT);
     assertThat(gApi.changes().id(r.getChangeId()).get().messages)
diff --git a/javatests/com/google/gerrit/acceptance/edit/ChangeEditIT.java b/javatests/com/google/gerrit/acceptance/edit/ChangeEditIT.java
index b0f183e..2883d8c 100644
--- a/javatests/com/google/gerrit/acceptance/edit/ChangeEditIT.java
+++ b/javatests/com/google/gerrit/acceptance/edit/ChangeEditIT.java
@@ -59,6 +59,7 @@
 import com.google.gerrit.extensions.common.EditInfo;
 import com.google.gerrit.extensions.common.FileInfo;
 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.ResourceConflictException;
 import com.google.gerrit.server.ChangeMessagesUtil;
@@ -436,6 +437,16 @@
   }
 
   @Test
+  public void renameExistingFileToInvalidPath() throws Exception {
+    createEmptyEditFor(changeId);
+    BadRequestException badRequest =
+        assertThrows(
+            BadRequestException.class,
+            () -> gApi.changes().id(changeId).edit().renameFile(FILE_NAME, "invalid/path/"));
+    assertThat(badRequest.getMessage()).isEqualTo("Invalid path: invalid/path/");
+  }
+
+  @Test
   public void createEditByDeletingExistingFileRest() throws Exception {
     adminRestSession.delete(urlEditFile(changeId, FILE_NAME)).assertNoContent();
     assertThat(getFileContentOfEdit(changeId, FILE_NAME)).isAbsent();
diff --git a/javatests/com/google/gerrit/acceptance/server/git/receive/ReceiveCommitsCommentValidationIT.java b/javatests/com/google/gerrit/acceptance/server/git/receive/ReceiveCommitsCommentValidationIT.java
index d8b65b7..ccfe783 100644
--- a/javatests/com/google/gerrit/acceptance/server/git/receive/ReceiveCommitsCommentValidationIT.java
+++ b/javatests/com/google/gerrit/acceptance/server/git/receive/ReceiveCommitsCommentValidationIT.java
@@ -32,6 +32,7 @@
 import com.google.gerrit.extensions.config.FactoryModule;
 import com.google.gerrit.extensions.validators.CommentForValidation;
 import com.google.gerrit.extensions.validators.CommentForValidation.CommentType;
+import com.google.gerrit.extensions.validators.CommentValidationContext;
 import com.google.gerrit.extensions.validators.CommentValidator;
 import com.google.gerrit.testing.TestCommentHelper;
 import com.google.inject.Inject;
@@ -53,6 +54,7 @@
   private static final String COMMENT_TEXT = "The comment text";
 
   @Captor private ArgumentCaptor<ImmutableList<CommentForValidation>> capture;
+  @Captor private ArgumentCaptor<CommentValidationContext> captureCtx;
 
   @Override
   public Module createModule() {
@@ -76,14 +78,18 @@
 
   @Test
   public void validateComments_commentOK() throws Exception {
+    PushOneCommit.Result result = createChange();
+    String changeId = result.getChangeId();
+    String revId = result.getCommit().getName();
     when(mockCommentValidator.validateComments(
+            CommentValidationContext.builder()
+                .changeId(result.getChange().getId().get())
+                .project(result.getChange().project().get())
+                .build(),
             ImmutableList.of(
                 CommentForValidation.create(
                     CommentForValidation.CommentType.FILE_COMMENT, COMMENT_TEXT))))
         .thenReturn(ImmutableList.of());
-    PushOneCommit.Result result = createChange();
-    String changeId = result.getChangeId();
-    String revId = result.getCommit().getName();
     DraftInput comment = testCommentHelper.newDraft(COMMENT_TEXT);
     testCommentHelper.addDraft(changeId, revId, comment);
     assertThat(testCommentHelper.getPublishedComments(result.getChangeId())).isEmpty();
@@ -97,14 +103,18 @@
   public void validateComments_commentRejected() throws Exception {
     CommentForValidation commentForValidation =
         CommentForValidation.create(CommentType.FILE_COMMENT, COMMENT_TEXT);
+    PushOneCommit.Result result = createChange();
+    String changeId = result.getChangeId();
+    String revId = result.getCommit().getName();
     when(mockCommentValidator.validateComments(
+            CommentValidationContext.builder()
+                .changeId(result.getChange().getId().get())
+                .project(result.getChange().project().get())
+                .build(),
             ImmutableList.of(
                 CommentForValidation.create(
                     CommentForValidation.CommentType.FILE_COMMENT, COMMENT_TEXT))))
         .thenReturn(ImmutableList.of(commentForValidation.failValidation("Oh no!")));
-    PushOneCommit.Result result = createChange();
-    String changeId = result.getChangeId();
-    String revId = result.getCommit().getName();
     DraftInput comment = testCommentHelper.newDraft(COMMENT_TEXT);
     testCommentHelper.addDraft(changeId, revId, comment);
     assertThat(testCommentHelper.getPublishedComments(result.getChangeId())).isEmpty();
@@ -116,7 +126,8 @@
 
   @Test
   public void validateComments_inlineVsFileComments_allOK() throws Exception {
-    when(mockCommentValidator.validateComments(capture.capture())).thenReturn(ImmutableList.of());
+    when(mockCommentValidator.validateComments(captureCtx.capture(), capture.capture()))
+        .thenReturn(ImmutableList.of());
     PushOneCommit.Result result = createChange();
     String changeId = result.getChangeId();
     String revId = result.getCommit().getName();
@@ -132,6 +143,9 @@
 
     assertThat(capture.getAllValues()).hasSize(1);
 
+    assertThat(captureCtx.getValue().getProject()).isEqualTo(result.getChange().project().get());
+    assertThat(captureCtx.getValue().getChangeId()).isEqualTo(result.getChange().getId().get());
+
     assertThat(capture.getAllValues().get(0))
         .containsExactly(
             CommentForValidation.create(
@@ -143,7 +157,7 @@
   @Test
   @GerritConfig(name = "change.maxCommentLength", value = "" + MAX_COMMENT_LENGTH)
   public void validateComments_enforceLimits_commentTooLarge() throws Exception {
-    when(mockCommentValidator.validateComments(any())).thenReturn(ImmutableList.of());
+    when(mockCommentValidator.validateComments(any(), any())).thenReturn(ImmutableList.of());
     PushOneCommit.Result result = createChange();
     String changeId = result.getChangeId();
     int commentLength = MAX_COMMENT_LENGTH + 1;
diff --git a/javatests/com/google/gerrit/acceptance/server/mail/MailProcessorIT.java b/javatests/com/google/gerrit/acceptance/server/mail/MailProcessorIT.java
index 5531709..2409f52 100644
--- a/javatests/com/google/gerrit/acceptance/server/mail/MailProcessorIT.java
+++ b/javatests/com/google/gerrit/acceptance/server/mail/MailProcessorIT.java
@@ -29,6 +29,7 @@
 import com.google.gerrit.extensions.common.CommentInfo;
 import com.google.gerrit.extensions.config.FactoryModule;
 import com.google.gerrit.extensions.validators.CommentForValidation;
+import com.google.gerrit.extensions.validators.CommentValidationContext;
 import com.google.gerrit.extensions.validators.CommentValidator;
 import com.google.gerrit.mail.MailMessage;
 import com.google.gerrit.mail.MailProcessingUtil;
@@ -70,7 +71,7 @@
   @BeforeClass
   public static void setUpMock() {
     // Let the mock comment validator accept all comments during test setup.
-    when(mockCommentValidator.validateComments(any())).thenReturn(ImmutableList.of());
+    when(mockCommentValidator.validateComments(any(), any())).thenReturn(ImmutableList.of());
   }
 
   @Before
@@ -274,7 +275,8 @@
         MailProcessingUtil.rfcDateformatter.format(
             ZonedDateTime.ofInstant(comments.get(0).updated.toInstant(), ZoneId.of("UTC")));
 
-    setupFailValidation(CommentForValidation.CommentType.CHANGE_MESSAGE);
+    setupFailValidation(
+        CommentForValidation.CommentType.CHANGE_MESSAGE, changeInfo.project, changeInfo._number);
 
     MailMessage.Builder b = messageBuilderWithDefaultFields();
     String txt = newPlaintextBody(getChangeUrl(changeInfo) + "/1", COMMENT_TEXT, null, null, null);
@@ -298,7 +300,8 @@
         MailProcessingUtil.rfcDateformatter.format(
             ZonedDateTime.ofInstant(comments.get(0).updated.toInstant(), ZoneId.of("UTC")));
 
-    setupFailValidation(CommentForValidation.CommentType.INLINE_COMMENT);
+    setupFailValidation(
+        CommentForValidation.CommentType.INLINE_COMMENT, changeInfo.project, changeInfo._number);
 
     MailMessage.Builder b = messageBuilderWithDefaultFields();
     String txt = newPlaintextBody(getChangeUrl(changeInfo) + "/1", null, COMMENT_TEXT, null, null);
@@ -322,7 +325,8 @@
         MailProcessingUtil.rfcDateformatter.format(
             ZonedDateTime.ofInstant(comments.get(0).updated.toInstant(), ZoneId.of("UTC")));
 
-    setupFailValidation(CommentForValidation.CommentType.FILE_COMMENT);
+    setupFailValidation(
+        CommentForValidation.CommentType.FILE_COMMENT, changeInfo.project, changeInfo._number);
 
     MailMessage.Builder b = messageBuilderWithDefaultFields();
     String txt = newPlaintextBody(getChangeUrl(changeInfo) + "/1", null, null, COMMENT_TEXT, null);
@@ -341,10 +345,12 @@
     return canonicalWebUrl.get() + "c/" + changeInfo.project + "/+/" + changeInfo._number;
   }
 
-  private void setupFailValidation(CommentForValidation.CommentType type) {
+  private void setupFailValidation(
+      CommentForValidation.CommentType type, String failProject, int failChange) {
     CommentForValidation commentForValidation = CommentForValidation.create(type, COMMENT_TEXT);
 
     when(mockCommentValidator.validateComments(
+            CommentValidationContext.builder().changeId(failChange).project(failProject).build(),
             ImmutableList.of(CommentForValidation.create(type, COMMENT_TEXT))))
         .thenReturn(ImmutableList.of(commentForValidation.failValidation("Oh no!")));
   }
diff --git a/javatests/com/google/gerrit/pgm/init/LibrariesTest.java b/javatests/com/google/gerrit/pgm/init/LibrariesTest.java
deleted file mode 100644
index 5aa4718..0000000
--- a/javatests/com/google/gerrit/pgm/init/LibrariesTest.java
+++ /dev/null
@@ -1,46 +0,0 @@
-// Copyright (C) 2009 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.pgm.init;
-
-import static org.junit.Assert.assertNotNull;
-import static org.mockito.Mockito.verifyZeroInteractions;
-
-import com.google.gerrit.pgm.init.api.ConsoleUI;
-import com.google.gerrit.server.config.SitePaths;
-import java.nio.file.Paths;
-import java.util.Collections;
-import org.junit.Test;
-import org.junit.runner.RunWith;
-import org.mockito.Mock;
-import org.mockito.junit.MockitoJUnitRunner;
-
-@RunWith(MockitoJUnitRunner.class)
-public class LibrariesTest {
-  @Mock ConsoleUI ui;
-  @Mock StaleLibraryRemover remover;
-
-  @Test
-  public void create() throws Exception {
-    final SitePaths site = new SitePaths(Paths.get("."));
-
-    Libraries lib =
-        new Libraries(
-            () -> new LibraryDownloader(ui, site, remover), Collections.emptyList(), false);
-
-    assertNotNull(lib.mysqlDriver);
-    verifyZeroInteractions(ui);
-    verifyZeroInteractions(remover);
-  }
-}
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.html b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.html
index f4bd6a6..283bd74 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.html
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.html
@@ -205,6 +205,9 @@
       <gr-confirm-revert-dialog id="confirmRevertDialog"
           class="confirmDialog"
           on-confirm="_handleRevertDialogConfirm"
+          commit-message="[[commitMessage]]"
+          change="[[change]]"
+          changes="[[_revertChanges]]"
           on-cancel="_handleConfirmDialogCancel"
           hidden></gr-confirm-revert-dialog>
       <gr-confirm-revert-submission-dialog id="confirmRevertSubmissionDialog"
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
index 2c4ca82..a4ed899 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
@@ -192,6 +192,11 @@
   const AWAIT_CHANGE_ATTEMPTS = 5;
   const AWAIT_CHANGE_TIMEOUT_MS = 1000;
 
+  const REVERT_TYPES = {
+    REVERT_SINGLE_CHANGE: 1,
+    REVERT_SUBMISSION: 2,
+  };
+
   /**
    * @appliesMixin Gerrit.FireMixin
    * @appliesMixin Gerrit.PatchSetMixin
@@ -421,6 +426,7 @@
           type: Boolean,
           value: true,
         },
+        _revertChanges: Array,
       };
     }
 
@@ -915,16 +921,13 @@
       return null;
     }
 
-    _modifyRevertMsg() {
-      return this.$.jsAPI.modifyRevertMsg(this.change,
-          this.$.confirmRevertDialog.message, this.commitMessage);
-    }
-
     showRevertDialog() {
-      this.$.confirmRevertDialog.populateRevertMessage(
-          this.commitMessage, this.change.current_revision);
-      this.$.confirmRevertDialog.message = this._modifyRevertMsg();
-      this._showActionDialog(this.$.confirmRevertDialog);
+      const query = 'submissionid:' + this.change.submission_id;
+      this.$.restAPI.getChanges('', query)
+          .then(changes => {
+            this._revertChanges = changes;
+            this._showActionDialog(this.$.confirmRevertDialog);
+          });
     }
 
     showRevertSubmissionDialog() {
@@ -932,7 +935,7 @@
       this.$.restAPI.getChanges('', query)
           .then(changes => {
             this.$.confirmRevertSubmissionDialog.
-                populateRevertSubmissionMessage(
+                _populateRevertSubmissionMessage(
                     this.commitMessage, this.change, changes);
             this._showActionDialog(this.$.confirmRevertSubmissionDialog);
           });
@@ -1143,20 +1146,24 @@
       );
     }
 
-    _handleRevertDialogConfirm() {
+    _handleRevertDialogConfirm(e) {
+      const revertType = e.detail.revertType;
+      const message = e.detail.message;
       const el = this.$.confirmRevertDialog;
       this.$.overlay.close();
       el.hidden = true;
-      this._fireAction('/revert', this.actions.revert, false,
-          {message: el.message});
-    }
-
-    _handleRevertSubmissionDialogConfirm() {
-      const el = this.$.confirmRevertSubmissionDialog;
-      this.$.overlay.close();
-      el.hidden = true;
-      this._fireAction('/revert_submission', this.actions.revert_submission,
-          false, {message: el.message});
+      switch (revertType) {
+        case REVERT_TYPES.REVERT_SINGLE_CHANGE:
+          this._fireAction('/revert', this.actions.revert, false,
+              {message});
+          break;
+        case REVERT_TYPES.REVERT_SUBMISSION:
+          this._fireAction('/revert_submission', this.actions.revert_submission,
+              false, {message});
+          break;
+        default:
+          console.error('invalid revert type');
+      }
     }
 
     _handleAbandonDialogConfirm() {
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.html b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.html
index 1c894ee..9c1a527 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.html
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.html
@@ -37,6 +37,7 @@
 </test-fixture>
 
 <script>
+  // TODO(dhruvsri): remove use of _populateRevertMessage as it's private
   suite('gr-change-actions tests', () => {
     let element;
     let sandbox;
@@ -795,12 +796,12 @@
     });
 
     suite('revert change', () => {
-      let alertStub;
       let fireActionStub;
 
       setup(() => {
         fireActionStub = sandbox.stub(element, '_fireAction');
-        alertStub = sandbox.stub(window, 'alert');
+        element.commitMessage = 'random commit message';
+        element.change.current_revision = 'abcdef';
         element.actions = {
           revert: {
             method: 'POST',
@@ -813,50 +814,149 @@
       });
 
       test('revert change with plugin hook', done => {
+        const newRevertMsg = 'Modified revert msg';
+        sandbox.stub(element.$.confirmRevertDialog, '_modifyRevertMsg',
+            () => newRevertMsg);
         element.change = {
           current_revision: 'abc1234',
         };
-        const newRevertMsg = 'Modified revert msg';
-        sandbox.stub(element, '_modifyRevertMsg',
-            () => newRevertMsg);
-        sandbox.stub(element.$.confirmRevertDialog, 'populateRevertMessage',
-            () => 'original msg');
+        sandbox.stub(element.$.confirmRevertDialog,
+            '_populateRevertSubmissionMessage', () => 'original msg');
         flush(() => {
-          const revertButton =
-              element.$$('gr-button[data-action-key="revert"]');
+          const revertButton = element.shadowRoot
+              .querySelector('gr-button[data-action-key="revert"]');
           MockInteractions.tap(revertButton);
-
-          assert.equal(element.$.confirmRevertDialog.message, newRevertMsg);
-          done();
+          flush(() => {
+            assert.equal(element.$.confirmRevertDialog.message, newRevertMsg);
+            done();
+          });
         });
       });
 
-      test('works', () => {
-        element.change = {
-          current_revision: 'abc1234',
-        };
-        sandbox.stub(element.$.confirmRevertDialog, 'populateRevertMessage',
-            () => 'original msg');
-        const revertButton = element.$$('gr-button[data-action-key="revert"]');
-        MockInteractions.tap(revertButton);
+      suite('revert change submitted together', () => {
+        setup(() => {
+          element.change = {
+            submission_id: '199',
+            current_revision: '2000',
+          };
+          sandbox.stub(element.$.restAPI, 'getChanges')
+              .returns(Promise.resolve([
+                {change_id: '12345678901234', topic: 'T', subject: 'random'},
+                {change_id: '23456', topic: 'T', subject: 'a'.repeat(100)},
+              ]));
+        });
 
-        element.$.confirmRevertDialog.message = 'foo message';
-        element._handleRevertDialogConfirm();
-        assert.notOk(alertStub.called);
+        test('confirm revert dialog shows both options', done => {
+          const revertButton = element.shadowRoot
+              .querySelector('gr-button[data-action-key="revert"]');
+          MockInteractions.tap(revertButton);
+          flush(() => {
+            const confirmRevertDialog = element.$.confirmRevertDialog;
+            const revertSingleChangeLabel = confirmRevertDialog
+                .shadowRoot.querySelector('.revertSingleChange');
+            const revertSubmissionLabel = confirmRevertDialog.
+                shadowRoot.querySelector('.revertSubmission');
+            assert(revertSingleChangeLabel.innerText.trim() ===
+                'Revert single change');
+            assert(revertSubmissionLabel.innerText.trim() ===
+                'Revert entire submission (2 Changes)');
+            let expectedMsg = 'Revert submission 199' + '\n\n' +
+              'Reason for revert: <INSERT REASONING HERE>' + '\n' +
+              'Reverted Changes:' + '\n' +
+              '1234567890:random' + '\n' +
+              '23456:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa...' +
+              '\n';
+            assert.equal(confirmRevertDialog.message, expectedMsg);
+            const radioInputs = confirmRevertDialog.shadowRoot
+                .querySelectorAll('input[name="revertOptions"]');
+            MockInteractions.tap(radioInputs[0]);
+            flush(() => {
+              expectedMsg = 'Revert "random commit message"\n\nThis reverts '
+               + 'commit 2000.\n\nReason'
+               + ' for revert: <INSERT REASONING HERE>\n';
+              assert.equal(confirmRevertDialog.message, expectedMsg);
+              done();
+            });
+          });
+        });
 
-        const action = {
-          __key: 'revert',
-          __type: 'change',
-          __primary: false,
-          enabled: true,
-          label: 'Revert',
-          method: 'POST',
-          title: 'Revert the change',
-        };
-        assert.deepEqual(fireActionStub.lastCall.args, [
-          '/revert', action, false, {
-            message: 'foo message',
-          }]);
+        test('message modification is retained on switching', done => {
+          const revertButton = element.shadowRoot
+              .querySelector('gr-button[data-action-key="revert"]');
+          const confirmRevertDialog = element.$.confirmRevertDialog;
+          MockInteractions.tap(revertButton);
+          flush(() => {
+            const radioInputs = confirmRevertDialog.shadowRoot
+                .querySelectorAll('input[name="revertOptions"]');
+            const revertSubmissionMsg = 'Revert submission 199' + '\n\n' +
+            'Reason for revert: <INSERT REASONING HERE>' + '\n' +
+            'Reverted Changes:' + '\n' +
+            '1234567890:random' + '\n' +
+            '23456:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa...' +
+            '\n';
+            const singleChangeMsg =
+            'Revert "random commit message"\n\nThis reverts '
+              + 'commit 2000.\n\nReason'
+              + ' for revert: <INSERT REASONING HERE>\n';
+            assert.equal(confirmRevertDialog.message, revertSubmissionMsg);
+            const newRevertMsg = revertSubmissionMsg + 'random';
+            const newSingleChangeMsg = singleChangeMsg + 'random';
+            confirmRevertDialog.message = newRevertMsg;
+            MockInteractions.tap(radioInputs[0]);
+            flush(() => {
+              assert.equal(confirmRevertDialog.message, singleChangeMsg);
+              confirmRevertDialog.message = newSingleChangeMsg;
+              MockInteractions.tap(radioInputs[1]);
+              flush(() => {
+                assert.equal(confirmRevertDialog.message, newRevertMsg);
+                MockInteractions.tap(radioInputs[0]);
+                flush(() => {
+                  assert.equal(confirmRevertDialog.message, newSingleChangeMsg);
+                  done();
+                });
+              });
+            });
+          });
+        });
+      });
+
+      suite('revert single change', () => {
+        setup(() => {
+          element.change = {
+            submission_id: '199',
+            current_revision: '2000',
+          };
+          sandbox.stub(element.$.restAPI, 'getChanges')
+              .returns(Promise.resolve([
+                {change_id: '12345678901234', topic: 'T', subject: 'random'},
+              ]));
+        });
+
+        test('confirm revert dialog shows one radio button', done => {
+          const revertButton = element.shadowRoot
+              .querySelector('gr-button[data-action-key="revert"]');
+          MockInteractions.tap(revertButton);
+          flush(() => {
+            const confirmRevertDialog = element.$.confirmRevertDialog;
+            const radioInputs = confirmRevertDialog.shadowRoot
+                .querySelectorAll('input[name="revertOptions"]');
+            assert.equal(radioInputs.length, 1);
+            const msg = 'Revert "random commit message"\n\n'
+              + 'This reverts commit 2000.\n\nReason '
+              + 'for revert: <INSERT REASONING HERE>\n';
+            assert.equal(confirmRevertDialog.message, msg);
+            const confirmButton = element.$.confirmRevertDialog.shadowRoot
+                .querySelector('gr-dialog')
+                .shadowRoot.querySelector('#confirm');
+            MockInteractions.tap(confirmButton);
+            flush(() => {
+              assert.equal(fireActionStub.getCall(0).args[0], '/revert');
+              assert.equal(fireActionStub.getCall(0).args[1].__key, 'revert');
+              assert.equal(fireActionStub.getCall(0).args[3].message, msg);
+              done();
+            });
+          });
+        });
       });
     });
 
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html
index fc3a8c1..7bffe8a 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html
+++ b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html
@@ -21,6 +21,7 @@
 <link rel="import" href="../../shared/gr-dialog/gr-dialog.html">
 <link rel="import" href="../../../styles/shared-styles.html">
 <link rel="import" href="../../plugins/gr-endpoint-decorator/gr-endpoint-decorator.html">
+<link rel="import" href="../../shared/gr-js-api-interface/gr-js-api-interface.html">
 
 <dom-module id="gr-confirm-revert-dialog">
   <template>
@@ -37,6 +38,13 @@
         display: block;
         width: 100%;
       }
+      .revertSubmissionLayout {
+        display: flex;
+      }
+      .label {
+        margin-left: var(--spacing-m);
+        margin-bottom: var(--spacing-m);
+      }
       iron-autogrow-textarea {
         font-family: var(--monospace-font-family);
         font-size: var(--font-size-mono);
@@ -50,7 +58,45 @@
         on-cancel="_handleCancelTap">
       <div class="header" slot="header">Revert Merged Change</div>
       <div class="main" slot="main">
+        <div class="revertSubmissionLayout">
+          <input
+            name="revertOptions"
+            type="radio"
+            id="revertSingleChange"
+            on-change="_handleRevertSingleChangeClicked"
+            checked="[[_computeIfSingleRevert(_revertType)]]">
+          <label for="revertSingleChange" class="label revertSingleChange">
+            Revert single change
+          </label>
+        </div>
+        <template is="dom-if" if="[[_showRevertSubmission]]">
+          <div on-click="_handleRevertSubmissionClicked" class="revertSubmissionLayout">
+            <input
+              name="revertOptions"
+              type="radio"
+              id="revertSubmission"
+              checked="[[_computeIfRevertSubmission(_revertType)]]">
+            <label for="revertSubmission" class="label revertSubmission">
+              Revert entire submission ([[changes.length]] Changes)
+            </label>
+        </template>
         <gr-endpoint-decorator name="confirm-revert-change">
+          <!-- Duplicating the text-area as a plugin in the case of a single
+          revert will override the entire textarea which should not happen
+          for multiple revert -->
+          <template is="dom-if" if="[[_computeIfSingleRevert(_revertType)]]">
+            <label for="messageInput">
+                Revert Commit Message
+              </label>
+            <iron-autogrow-textarea
+              id="messageInput"
+              class="message"
+              autocomplete="on"
+              max-rows="15"
+              bind-value="{{message}}"></iron-autogrow-textarea>
+          </template>
+        </gr-endpoint-decorator>
+        <template is="dom-if" if="[[_computeIfRevertSubmission(_revertType)]]">
           <label for="messageInput">
             Revert Commit Message
           </label>
@@ -60,9 +106,10 @@
               autocomplete="on"
               max-rows="15"
               bind-value="{{message}}"></iron-autogrow-textarea>
-        </gr-endpoint-decorator>
+        </template>
       </div>
     </gr-dialog>
+    <gr-js-api-interface id="jsAPI"></gr-js-api-interface>
   </template>
   <script src="gr-confirm-revert-dialog.js"></script>
 </dom-module>
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js
index bf727ec..438440e 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js
@@ -19,6 +19,13 @@
 
   const ERR_COMMIT_NOT_FOUND =
       'Unable to find the commit hash of this change.';
+  const CHANGE_SUBJECT_LIMIT = 50;
+
+  // TODO(dhruvsri): clean up repeated definitions after moving to js modules
+  const REVERT_TYPES = {
+    REVERT_SINGLE_CHANGE: 1,
+    REVERT_SUBMISSION: 2,
+  };
 
   /**
    * @appliesMixin Gerrit.FireMixin
@@ -45,12 +52,55 @@
     static get properties() {
       return {
         message: String,
+        _revertType: {
+          type: Number,
+          value: REVERT_TYPES.REVERT_SINGLE_CHANGE,
+        },
+        _showRevertSubmission: {
+          type: Boolean,
+          value: false,
+        },
+        changes: {
+          type: Array,
+          value() { return []; },
+        },
+        change: Object,
+        commitMessage: String,
       };
     }
 
-    populateRevertMessage(message, commitHash) {
+    static get observers() {
+      return [
+        'onInputUpdate(change, commitMessage, changes)',
+      ];
+    }
+
+    _computeIfSingleRevert(revertType) {
+      return revertType === REVERT_TYPES.REVERT_SINGLE_CHANGE;
+    }
+
+    _computeIfRevertSubmission(revertType) {
+      return revertType === REVERT_TYPES.REVERT_SUBMISSION;
+    }
+
+    _modifyRevertMsg(change, commitMessage, message) {
+      return this.$.jsAPI.modifyRevertMsg(change,
+          message, commitMessage);
+    }
+
+    onInputUpdate(change, commitMessage, changes) {
+      if (!change || !changes) return;
+      this._populateRevertSingleChangeMessage(
+          change, commitMessage, change.current_revision);
+      if (changes.length > 1) {
+        this._populateRevertSubmissionMessage(
+            change, changes);
+      }
+    }
+
+    _populateRevertSingleChangeMessage(change, commitMessage, commitHash) {
       // Figure out what the revert title should be.
-      const originalTitle = message.split('\n')[0];
+      const originalTitle = (commitMessage || '').split('\n')[0];
       const revertTitle = `Revert "${originalTitle}"`;
       if (!commitHash) {
         this.fire('show-alert', {message: ERR_COMMIT_NOT_FOUND});
@@ -58,20 +108,77 @@
       }
       const revertCommitText = `This reverts commit ${commitHash}.`;
 
-      this.message = `${revertTitle}\n\n${revertCommitText}\n\n` +
+      this.revertSingleChangeMessage =
+          `${revertTitle}\n\n${revertCommitText}\n\n` +
           `Reason for revert: <INSERT REASONING HERE>\n`;
+      // This is to give plugins a chance to update message
+      this.revertSingleChangeMessage =
+          this._modifyRevertMsg(change, commitMessage,
+              this.revertSingleChangeMessage);
+      this.message = this.revertSingleChangeMessage;
+    }
+
+    _getTrimmedChangeSubject(subject) {
+      if (!subject) return '';
+      if (subject.length < CHANGE_SUBJECT_LIMIT) return subject;
+      return subject.substring(0, CHANGE_SUBJECT_LIMIT) + '...';
+    }
+
+    _modifyRevertSubmissionMsg(change) {
+      return this.$.jsAPI.modifyRevertSubmissionMsg(change,
+          this.revertSubmissionMessage, this.commitMessage);
+    }
+
+    _populateRevertSubmissionMessage(change, changes) {
+      // Follow the same convention of the revert
+      const commitHash = change.current_revision;
+      if (!commitHash) {
+        this.fire('show-alert', {message: ERR_COMMIT_NOT_FOUND});
+        return;
+      }
+      if (!changes || changes.length <= 1) return;
+      const submissionId = change.submission_id;
+      const revertTitle = 'Revert submission ' + submissionId;
+      this.changes = changes;
+      this.revertSubmissionMessage = revertTitle + '\n\n' +
+          'Reason for revert: <INSERT REASONING HERE>\n';
+      this.revertSubmissionMessage += 'Reverted Changes:\n';
+      changes.forEach(change => {
+        this.revertSubmissionMessage += change.change_id.substring(0, 10) + ':'
+          + this._getTrimmedChangeSubject(change.subject) + '\n';
+      });
+      this.revertSubmissionMessage = this._modifyRevertSubmissionMsg(change);
+      this.message = this.revertSubmissionMessage;
+      this._revertType = REVERT_TYPES.REVERT_SUBMISSION;
+      this._showRevertSubmission = true;
+    }
+
+    _handleRevertSingleChangeClicked() {
+      if (this._revertType === REVERT_TYPES.REVERT_SINGLE_CHANGE) return;
+      this.revertSubmissionMessage = this.message;
+      this.message = this.revertSingleChangeMessage;
+      this._revertType = REVERT_TYPES.REVERT_SINGLE_CHANGE;
+    }
+
+    _handleRevertSubmissionClicked() {
+      if (this._revertType === REVERT_TYPES.REVERT_SUBMISSION) return;
+      this._revertType = REVERT_TYPES.REVERT_SUBMISSION;
+      this.revertSingleChangeMessage = this.message;
+      this.message = this.revertSubmissionMessage;
     }
 
     _handleConfirmTap(e) {
       e.preventDefault();
       e.stopPropagation();
-      this.fire('confirm', null, {bubbles: false});
+      this.fire('confirm', {revertType: this._revertType,
+        message: this.message}, {bubbles: false});
     }
 
     _handleCancelTap(e) {
       e.preventDefault();
       e.stopPropagation();
-      this.fire('cancel', null, {bubbles: false});
+      this.fire('cancel', {revertType: this._revertType},
+          {bubbles: false});
     }
   }
 
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog_test.html b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog_test.html
index dbdfba2..1d28d32 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog_test.html
+++ b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog_test.html
@@ -50,13 +50,14 @@
       assert.isNotOk(element.message);
       const alertStub = sandbox.stub();
       element.addEventListener('show-alert', alertStub);
-      element.populateRevertMessage('not a commitHash in sight', undefined);
+      element._populateRevertSingleChangeMessage({},
+          'not a commitHash in sight', undefined);
       assert.isTrue(alertStub.calledOnce);
     });
 
     test('single line', () => {
       assert.isNotOk(element.message);
-      element.populateRevertMessage(
+      element._populateRevertSingleChangeMessage({},
           'one line commit\n\nChange-Id: abcdefg\n',
           'abcd123');
       const expected = 'Revert "one line commit"\n\n' +
@@ -67,7 +68,7 @@
 
     test('multi line', () => {
       assert.isNotOk(element.message);
-      element.populateRevertMessage(
+      element._populateRevertSingleChangeMessage({},
           'many lines\ncommit\n\nmessage\n\nChange-Id: abcdefg\n',
           'abcd123');
       const expected = 'Revert "many lines"\n\n' +
@@ -78,7 +79,7 @@
 
     test('issue above change id', () => {
       assert.isNotOk(element.message);
-      element.populateRevertMessage(
+      element._populateRevertSingleChangeMessage({},
           'much lines\nvery\n\ncommit\n\nBug: Issue 42\nChange-Id: abcdefg\n',
           'abcd123');
       const expected = 'Revert "much lines"\n\n' +
@@ -89,7 +90,7 @@
 
     test('revert a revert', () => {
       assert.isNotOk(element.message);
-      element.populateRevertMessage(
+      element._populateRevertSingleChangeMessage({},
           'Revert "one line commit"\n\nChange-Id: abcdefg\n',
           'abcd123');
       const expected = 'Revert "Revert "one line commit""\n\n' +
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-submission-dialog/gr-confirm-revert-submission-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-revert-submission-dialog/gr-confirm-revert-submission-dialog.js
index d59f5cd..ae8dfa5 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-revert-submission-dialog/gr-confirm-revert-submission-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-revert-submission-dialog/gr-confirm-revert-submission-dialog.js
@@ -50,7 +50,7 @@
       };
     }
 
-    getTrimmedChangeSubject(subject) {
+    _getTrimmedChangeSubject(subject) {
       if (!subject) return '';
       if (subject.length < CHANGE_SUBJECT_LIMIT) return subject;
       return subject.substring(0, CHANGE_SUBJECT_LIMIT) + '...';
@@ -61,7 +61,7 @@
           this.message, this.commitMessage);
     }
 
-    populateRevertSubmissionMessage(message, change, changes) {
+    _populateRevertSubmissionMessage(message, change, changes) {
       // Follow the same convention of the revert
       const commitHash = change.current_revision;
       if (!commitHash) {
@@ -77,7 +77,7 @@
       changes = changes || [];
       changes.forEach(change => {
         this.message += change.change_id.substring(0, 10) + ': ' +
-          this.getTrimmedChangeSubject(change.subject) + '\n';
+          this._getTrimmedChangeSubject(change.subject) + '\n';
       });
       this.message = this._modifyRevertSubmissionMsg(change);
     }
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-submission-dialog/gr-confirm-revert-submission-dialog_test.html b/polygerrit-ui/app/elements/change/gr-confirm-revert-submission-dialog/gr-confirm-revert-submission-dialog_test.html
index cc4bd54..af99c7e 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-revert-submission-dialog/gr-confirm-revert-submission-dialog_test.html
+++ b/polygerrit-ui/app/elements/change/gr-confirm-revert-submission-dialog/gr-confirm-revert-submission-dialog_test.html
@@ -51,7 +51,7 @@
       assert.isNotOk(element.message);
       const alertStub = sandbox.stub();
       element.addEventListener('show-alert', alertStub);
-      element.populateRevertSubmissionMessage(
+      element._populateRevertSubmissionMessage(
           'not a commitHash in sight'
       );
       assert.isTrue(alertStub.calledOnce);
@@ -59,7 +59,7 @@
 
     test('single line', () => {
       assert.isNotOk(element.message);
-      element.populateRevertSubmissionMessage(
+      element._populateRevertSubmissionMessage(
           'one line commit\n\nChange-Id: abcdefg\n',
           'abcd123');
       const expected = 'Revert submission\n\n' +
@@ -69,7 +69,7 @@
 
     test('multi line', () => {
       assert.isNotOk(element.message);
-      element.populateRevertSubmissionMessage(
+      element._populateRevertSubmissionMessage(
           'many lines\ncommit\n\nmessage\n\nChange-Id: abcdefg\n',
           'abcd123');
       const expected = 'Revert submission\n\n' +
@@ -79,7 +79,7 @@
 
     test('issue above change id', () => {
       assert.isNotOk(element.message);
-      element.populateRevertSubmissionMessage(
+      element._populateRevertSubmissionMessage(
           'test \nvery\n\ncommit\n\nBug: Issue 42\nChange-Id: abcdefg\n',
           'abcd123');
       const expected = 'Revert submission\n\n' +
@@ -89,7 +89,7 @@
 
     test('revert a revert', () => {
       assert.isNotOk(element.message);
-      element.populateRevertSubmissionMessage(
+      element._populateRevertSubmissionMessage(
           'Revert "one line commit"\n\nChange-Id: abcdefg\n',
           'abcd123');
       const expected = 'Revert submission\n\n' +
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.js b/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.js
index 359a039..e46f959 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.js
@@ -192,15 +192,20 @@
       }
     }
 
-    /**
-     * For Polymer 2, use shadowRoot.getSelection instead.
-     */
     _getSelection() {
-      const diffHost = util.querySelector(document.body, 'gr-diff');
-      const selection = diffHost &&
-        diffHost.shadowRoot &&
-        diffHost.shadowRoot.getSelection();
-      return selection ? selection: window.getSelection();
+      const diffHosts = util.querySelectorAll(document.body, 'gr-diff');
+      if (!diffHosts.length) return window.getSelection();
+
+      const curDiffHost = diffHosts.find(diffHost => {
+        if (!diffHost || !diffHost.shadowRoot) return false;
+        const selection = diffHost.shadowRoot.getSelection();
+        // Pick the one with valid selection:
+        // https://developer.mozilla.org/en-US/docs/Web/API/Selection/type
+        return selection && selection.type !== 'None';
+      });
+
+      return curDiffHost ?
+        curDiffHost.shadowRoot.getSelection(): window.getSelection();
     }
 
     /**
diff --git a/polygerrit-ui/app/scripts/util.js b/polygerrit-ui/app/scripts/util.js
index 672c43f..565b9b3 100644
--- a/polygerrit-ui/app/scripts/util.js
+++ b/polygerrit-ui/app/scripts/util.js
@@ -105,7 +105,7 @@
    */
   util.querySelector = (el, selector) => {
     let nodes = [el];
-    let element = null;
+    let result = null;
     while (nodes.length) {
       const node = nodes.pop();
 
@@ -113,19 +113,49 @@
       if (!node || !node.querySelector) continue;
 
       // Try find it with native querySelector directly
-      element = node.querySelector(selector);
+      result = node.querySelector(selector);
 
-      if (element) {
+      if (result) {
         break;
-      } else if (node.shadowRoot) {
-        // If shadowHost detected, add the host and its children
-        nodes = nodes.concat(Array.from(node.children));
-        nodes.push(node.shadowRoot);
-      } else {
-        nodes = nodes.concat(Array.from(node.children));
       }
+
+      // Add all nodes with shadowRoot and loop through
+      const allShadowNodes = [...node.querySelectorAll('*')]
+          .filter(child => !!child.shadowRoot)
+          .map(child => child.shadowRoot);
+      nodes = nodes.concat(allShadowNodes);
     }
-    return element;
+    return result;
+  };
+
+  /**
+   * Query selector all dom elements matching with certain selector.
+   *
+   * This is shadow DOM compatible, but only works when selector is within
+   * one shadow host, won't work if your selector is crossing
+   * multiple shadow hosts.
+   *
+   * Note: this can be very expensive, only use when have to.
+   */
+  util.querySelectorAll = (el, selector) => {
+    let nodes = [el];
+    const results = new Set();
+    while (nodes.length) {
+      const node = nodes.pop();
+
+      if (!node || !node.querySelectorAll) continue;
+
+      // Try find all from regular children
+      [...node.querySelectorAll(selector)]
+          .forEach(el => results.add(el));
+
+      // Add all nodes with shadowRoot and loop through
+      const allShadowNodes = [...node.querySelectorAll('*')]
+          .filter(child => !!child.shadowRoot)
+          .map(child => child.shadowRoot);
+      nodes = nodes.concat(allShadowNodes);
+    }
+    return [...results];
   };
 
   window.util = util;
diff --git a/resources/com/google/gerrit/pgm/init/libraries.config b/resources/com/google/gerrit/pgm/init/libraries.config
deleted file mode 100644
index 3d3545b..0000000
--- a/resources/com/google/gerrit/pgm/init/libraries.config
+++ /dev/null
@@ -1,50 +0,0 @@
-# Copyright (C) 2009 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.
-
-[library "mysqlDriver"]
-  name = MySQL Connector/J 5.1.43
-  url = https://repo1.maven.org/maven2/mysql/mysql-connector-java/5.1.43/mysql-connector-java-5.1.43.jar
-  sha1 = dee9103eec0d877f3a21c82d4d9e9f4fbd2d6e0a
-  remove = mysql-connector-java-.*[.]jar
-
-[library "mariadbDriver"]
-  name = MariaDB Connector/J 2.3.0
-  url = https://repo1.maven.org/maven2/org/mariadb/jdbc/mariadb-java-client/2.3.0/mariadb-java-client-2.3.0.jar
-  sha1 = c2b1a6002a169757d0649449288e9b3b776af76b
-  remove = mariadb-java-client-.*[.]jar
-
-[library "oracleDriver"]
-  name = Oracle JDBC driver 11g Release 2 (11.2.0)
-  url = file:///u01/app/oracle/product/11.2.0/xe/jdbc/lib/ojdbc6.jar
-  sha1 = 2f89cd9176772c3a6c261ce6a8e3d0d4425f5679
-  remove = ojdbc6.jar
-
-[library "db2Driver"]
-  name = DB2 Type 4 JDBC driver (10.5)
-  url = file:///opt/ibm/db2/V10.5/java/db2jcc4.jar
-  sha1 = 9344d4fd41d6511f2d1d1deb7759056495b3a39b
-  needs = db2DriverLicense
-  remove = db2jcc4.jar
-
-# Omit SHA-1 for license JAR as it's not stable and depends on the product
-# the customer has purchased.
-[library "db2DriverLicense"]
-  name = DB2 Type 4 JDBC driver license (10.5)
-  url = file:///opt/ibm/db2/V10.5/java/db2jcc_license_cu.jar
-  remove = db2jcc_license_cu.jar
-
-[library "hanaDriver"]
-  name = HANA JDBC driver
-  url = file:///usr/sap/hdbclient/ngdbc.jar
-  remove = ngdbc.jar