diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index d897210..3f0c751 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -2052,7 +2052,7 @@
 comments for each path are sorted by patch set number. Each comment has
 the `patch_set` and `author` fields set.
 
-If the `enable_context` request parameter is set to true, the comment entries
+If the `enable-context` request parameter is set to true, the comment entries
 will contain a list of link:#context-line[ContextLine] containing the lines of
 the source file where the comment was written.
 
@@ -6699,7 +6699,7 @@
 this comment applies.
 |`context_lines` |optional|
 A list of link:#context-line[ContextLine] containing the lines of the source
-file where the comment was written. Available only if the "enable_context"
+file where the comment was written. Available only if the "enable-context"
 parameter (see link:#list-change-comments[List Change Comments]) is set.
 
 |===========================
diff --git a/java/com/google/gerrit/acceptance/PushOneCommit.java b/java/com/google/gerrit/acceptance/PushOneCommit.java
index afd451a..4215255 100644
--- a/java/com/google/gerrit/acceptance/PushOneCommit.java
+++ b/java/com/google/gerrit/acceptance/PushOneCommit.java
@@ -43,8 +43,12 @@
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicInteger;
 import org.eclipse.jgit.api.TagCommand;
+import org.eclipse.jgit.dircache.DirCacheEditor.PathEdit;
+import org.eclipse.jgit.dircache.DirCacheEntry;
 import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.FileMode;
 import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.revwalk.RevBlob;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.transport.PushResult;
 import org.eclipse.jgit.transport.RemoteRefUpdate;
@@ -277,6 +281,19 @@
     return this;
   }
 
+  public PushOneCommit addSymlink(String path, String target) throws Exception {
+    RevBlob blobId = testRepo.blob(target);
+    commitBuilder.edit(
+        new PathEdit(path) {
+          @Override
+          public void apply(DirCacheEntry ent) {
+            ent.setFileMode(FileMode.SYMLINK);
+            ent.setObjectId(blobId);
+          }
+        });
+    return this;
+  }
+
   public Result to(String ref) throws Exception {
     for (Map.Entry<String, String> e : files.entrySet()) {
       commitBuilder.add(e.getKey(), e.getValue());
diff --git a/java/com/google/gerrit/server/restapi/change/CommentJson.java b/java/com/google/gerrit/server/restapi/change/CommentJson.java
index cc8ad47..02f39ab 100644
--- a/java/com/google/gerrit/server/restapi/change/CommentJson.java
+++ b/java/com/google/gerrit/server/restapi/change/CommentJson.java
@@ -123,7 +123,6 @@
           list = new ArrayList<>();
           out.put(o.path, list);
         }
-        o.path = null;
         list.add(o);
       }
 
@@ -133,10 +132,11 @@
         loader.fill();
       }
 
+      List<T> allComments = out.values().stream().flatMap(Collection::stream).collect(toList());
       if (fillCommentContext) {
-        List<T> allComments = out.values().stream().flatMap(Collection::stream).collect(toList());
         addCommentContext(allComments);
       }
+      allComments.forEach(c -> c.path = null); // we don't need path since it exists in the map keys
       return out;
     }
 
diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java
index 39366bd..ff785a2 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java
@@ -2745,6 +2745,55 @@
   }
 
   @Test
+  public void symlinkConveredToRegularFileIsIdentifiedAsDeleted() throws Exception {
+    // TODO(ghareeb): See https://bugs.chromium.org/p/gerrit/issues/detail?id=13914.
+    // This test creates a corner scenario of replacing a symlink with a regular file
+    // of the same name. When both patchsets are diffed, the List Files endpoint identifies the
+    // file as a 'REWRITE', however the diff endpoint for the symlink file identifies the file as
+    // deleted. This case is a bit risky since it hides from the user the new content that was added
+    // in the new regular file. Ideally, the diff endpoint should show two entries for the deleted
+    // symlink and the added file, or only one entry "REWRITE" with the content that was added to
+    // the new file.
+    String target = "file.txt";
+    String symlink = "link.lnk";
+
+    // Create a change adding file "FileName" and a symlink "symLink" pointing to the file
+    PushOneCommit push =
+        pushFactory
+            .create(admin.newIdent(), testRepo, "Commit Subject", target, "content")
+            .addSymlink(symlink, target);
+
+    PushOneCommit.Result result = push.to("refs/for/master");
+    String initialRev = gApi.changes().id(result.getChangeId()).get().currentRevision;
+
+    // Delete the symlink with patchset 2
+    gApi.changes().id(result.getChangeId()).edit().deleteFile(symlink);
+    gApi.changes().id(result.getChangeId()).edit().publish();
+
+    // Re-add the symlink as a regular file with patchset 3
+    gApi.changes()
+        .id(result.getChangeId())
+        .edit()
+        .modifyFile(symlink, RawInputUtil.create("Content of the new file named 'symlink'"));
+    gApi.changes().id(result.getChangeId()).edit().publish();
+
+    Map<String, FileInfo> changedFiles =
+        gApi.changes().id(result.getChangeId()).current().files(initialRev);
+
+    assertThat(changedFiles.keySet()).containsExactly("/COMMIT_MSG", symlink);
+    assertThat(changedFiles.get(symlink).status).isEqualTo('W'); // Rewrite
+
+    DiffInfo diffInfo =
+        gApi.changes().id(result.getChangeId()).current().file(symlink).diff(initialRev);
+
+    // TODO(ghareeb): This is not a desired behaviour. The diff endpoint treats the file as
+    // 'DELETED', hence hiding any new content that was added to the new regular file. It is better
+    // to show the file as 'ADDED'. See https://bugs.chromium.org/p/gerrit/issues/detail?id=13914
+    // for more details.
+    assertThat(diffInfo.changeType).isEqualTo(ChangeType.DELETED);
+  }
+
+  @Test
   public void diffOfNonExistentFileIsAnEmptyDiffResult() throws Exception {
     addModifiedPatchSet(changeId, FILE_NAME, content -> content.replace("Line 2\n", "Line two\n"));
 
diff --git a/plugins/codemirror-editor b/plugins/codemirror-editor
index 7357ab4..740c35a 160000
--- a/plugins/codemirror-editor
+++ b/plugins/codemirror-editor
@@ -1 +1 @@
-Subproject commit 7357ab473599d16ae33cc982bbd65472f08c2dd6
+Subproject commit 740c35ae36f44748b3c91e60ee7dcb2fb6e99549
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts
index febf18a..fdf2811 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts
@@ -38,11 +38,7 @@
 import {GerritNav} from '../../core/gr-navigation/gr-navigation';
 import {getPluginLoader} from '../../shared/gr-js-api-interface/gr-plugin-loader';
 import {appContext} from '../../../services/app-context';
-import {
-  fetchChangeUpdates,
-  patchNumEquals,
-  CURRENT,
-} from '../../../utils/patch-set-util';
+import {fetchChangeUpdates, CURRENT} from '../../../utils/patch-set-util';
 import {
   changeIsOpen,
   isOwner,
@@ -1153,7 +1149,7 @@
 
   _getRevision(change: ChangeViewChangeInfo, patchNum?: PatchSetNum) {
     for (const rev of Object.values(change.revisions)) {
-      if (patchNumEquals(rev._number, patchNum)) {
+      if (rev._number === patchNum) {
         return rev;
       }
     }
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.js b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.js
index 0279b7e..f7bca82 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.js
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.js
@@ -258,7 +258,7 @@
           rev2: revObj,
         },
       };
-      assert.deepEqual(element._getRevision(change, '2'), revObj);
+      assert.deepEqual(element._getRevision(change, 2), revObj);
     });
 
     test('_actionComparator sort order', () => {
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
index 684891f..126d017 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
@@ -69,7 +69,6 @@
   fetchChangeUpdates,
   hasEditBasedOnCurrentPatchSet,
   hasEditPatchsetLoaded,
-  patchNumEquals,
   PatchSet,
 } from '../../../utils/patch-set-util';
 import {changeStatuses, changeStatusString} from '../../../utils/change-util';
@@ -1656,7 +1655,7 @@
     if (!this._change) throw new Error('missing required change property');
     if (!this._patchRange)
       throw new Error('missing required _patchRange property');
-    if (patchNumEquals(this._patchRange.basePatchNum, ParentPatchSetNum)) {
+    if (this._patchRange.basePatchNum === ParentPatchSetNum) {
       fireAlert(this, 'Base is already selected.');
       return;
     }
@@ -1670,7 +1669,7 @@
     if (!this._change) throw new Error('missing required change property');
     if (!this._patchRange)
       throw new Error('missing required _patchRange property');
-    if (patchNumEquals(this._patchRange.basePatchNum, ParentPatchSetNum)) {
+    if (this._patchRange.basePatchNum === ParentPatchSetNum) {
       fireAlert(this, 'Left is already base.');
       return;
     }
@@ -1685,7 +1684,7 @@
     if (!this._patchRange)
       throw new Error('missing required _patchRange property');
     const latestPatchNum = computeLatestPatchNum(this._allPatchSets);
-    if (patchNumEquals(this._patchRange.patchNum, latestPatchNum)) {
+    if (this._patchRange.patchNum === latestPatchNum) {
       fireAlert(this, 'Latest is already selected.');
       return;
     }
@@ -1704,7 +1703,7 @@
     const latestPatchNum = computeLatestPatchNum(this._allPatchSets);
     if (!this._patchRange)
       throw new Error('missing required _patchRange property');
-    if (patchNumEquals(this._patchRange.patchNum, latestPatchNum)) {
+    if (this._patchRange.patchNum === latestPatchNum) {
       fireAlert(this, 'Right is already latest.');
       return;
     }
@@ -1724,8 +1723,8 @@
       throw new Error('missing required _patchRange property');
     const latestPatchNum = computeLatestPatchNum(this._allPatchSets);
     if (
-      patchNumEquals(this._patchRange.patchNum, latestPatchNum) &&
-      patchNumEquals(this._patchRange.basePatchNum, ParentPatchSetNum)
+      this._patchRange.patchNum === latestPatchNum &&
+      this._patchRange.basePatchNum === ParentPatchSetNum
     ) {
       fireAlert(this, 'Already diffing base against latest.');
       return;
@@ -1967,7 +1966,7 @@
         if (
           !this._patchRange ||
           !this._patchRange.patchNum ||
-          patchNumEquals(this._patchRange.patchNum, currentRevision._number)
+          this._patchRange.patchNum === currentRevision._number
         ) {
           // CommitInfo.commit is optional, and may need patching.
           if (currentRevision.commit && !currentRevision.commit.commit) {
@@ -2567,7 +2566,7 @@
     }
 
     const patchRange = patchRangeRecord.base || {};
-    return patchNumEquals(patchRange.patchNum, EditPatchSetNum);
+    return patchRange.patchNum === EditPatchSetNum;
   }
 
   _handleFileActionTap(e: CustomEvent<{path: string; action: string}>) {
@@ -2651,10 +2650,7 @@
       throw new Error('missing required _patchRange property');
     let patchNum;
     if (
-      !patchNumEquals(
-        this._patchRange.patchNum,
-        computeLatestPatchNum(this._allPatchSets)
-      )
+      !(this._patchRange.patchNum === computeLatestPatchNum(this._allPatchSets))
     ) {
       patchNum = this._patchRange.patchNum;
     }
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.ts b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.ts
index 1195ea6..c4526bb 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.ts
@@ -246,8 +246,10 @@
   _computeDisableCherryPick(
     cherryPickType: CherryPickType,
     duplicateProjectChanges: boolean,
-    statuses: Statuses
+    statuses: Statuses,
+    branch?: BranchName
   ) {
+    if (!branch) return true;
     const duplicateProject =
       cherryPickType === CherryPickType.TOPIC && duplicateProjectChanges;
     if (duplicateProject) return true;
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog_html.ts b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog_html.ts
index 16262c6..4de395c 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog_html.ts
+++ b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog_html.ts
@@ -85,7 +85,7 @@
   <gr-dialog
     confirm-label="Cherry Pick"
     cancel-label="[[_computeCancelLabel(_statuses)]]"
-    disabled$="[[_computeDisableCherryPick(_cherryPickType, _duplicateProjectChanges, _statuses)]]"
+    disabled$="[[_computeDisableCherryPick(_cherryPickType, _duplicateProjectChanges, _statuses, branch)]]"
     on-confirm="_handleConfirmTap"
     on-cancel="_handleCancelTap"
   >
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog_test.js b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog_test.js
index ae34b70..5564fcf 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog_test.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog_test.js
@@ -174,6 +174,9 @@
     test('submit button is blocked while cherry picks is running', done => {
       const confirmButton = element.shadowRoot.querySelector('gr-dialog').$
           .confirm;
+      assert.isTrue(confirmButton.hasAttribute('disabled'));
+      element.branch = 'b';
+      flush();
       assert.isFalse(confirmButton.hasAttribute('disabled'));
       element.updateStatus(changes[0], {status: 'RUNNING'});
       flush(() => {
diff --git a/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.ts b/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.ts
index 27d9756..5949513 100644
--- a/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.ts
@@ -20,7 +20,6 @@
 import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
 import {PolymerElement} from '@polymer/polymer/polymer-element';
 import {htmlTemplate} from './gr-download-dialog_html';
-import {patchNumEquals} from '../../../utils/patch-set-util';
 import {changeBaseURL} from '../../../utils/change-util';
 import {customElement, property, computed, observe} from '@polymer/decorators';
 import {ChangeInfo, ServerInfo, PatchSetNum} from '../../../types/common';
@@ -72,7 +71,7 @@
     }
 
     for (const rev of Object.values(this.change.revisions || {})) {
-      if (patchNumEquals(rev._number, this.patchNum)) {
+      if (rev._number === this.patchNum) {
         const fetch = rev.fetch;
         if (fetch) {
           return Object.keys(fetch).sort();
@@ -113,7 +112,7 @@
     if (!change || !selectedScheme) return [];
     for (const rev of Object.values(change.revisions || {})) {
       if (
-        patchNumEquals(rev._number, patchNum) &&
+        rev._number === patchNum &&
         rev &&
         rev.fetch &&
         hasOwnProperty(rev.fetch, selectedScheme)
@@ -171,7 +170,7 @@
 
     let shortRev = '';
     for (const rev in change.revisions) {
-      if (patchNumEquals(change.revisions[rev]._number, patchNum)) {
+      if (change.revisions[rev]._number === patchNum) {
         shortRev = rev.substr(0, 7);
         break;
       }
@@ -185,7 +184,7 @@
       return false;
     }
     for (const rev of Object.values(change.revisions || {})) {
-      if (patchNumEquals(rev._number, patchNum)) {
+      if (rev._number === patchNum) {
         const parentLength =
           rev.commit && rev.commit.parents ? rev.commit.parents.length : 0;
         return parentLength === 0 || parentLength > 1;
diff --git a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.ts b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.ts
index 3c99648..146b3e2 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.ts
+++ b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.ts
@@ -35,7 +35,6 @@
 import {
   computeLatestPatchNum,
   getRevisionByPatchNum,
-  patchNumEquals,
   PatchSet,
 } from '../../../utils/patch-set-util';
 import {property, computed, observe, customElement} from '@polymer/decorators';
@@ -321,8 +320,7 @@
   _handlePatchChange(e: CustomEvent) {
     const {basePatchNum, patchNum} = e.detail;
     if (
-      (patchNumEquals(basePatchNum, this.basePatchNum) &&
-        patchNumEquals(patchNum, this.patchNum)) ||
+      (basePatchNum === this.basePatchNum && patchNum === this.patchNum) ||
       !this.change
     ) {
       return;
@@ -354,7 +352,7 @@
 
   _computePatchInfoClass(patchNum?: PatchSetNum, allPatchSets?: PatchSet[]) {
     const latestNum = computeLatestPatchNum(allPatchSets);
-    if (patchNumEquals(patchNum, latestNum)) {
+    if (patchNum === latestNum) {
       return '';
     }
     return 'patchInfoOldPatchSet';
diff --git a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header_test.js b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header_test.js
index cee0262..b8670c0 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header_test.js
+++ b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header_test.js
@@ -249,11 +249,11 @@
 
   test('class is applied to file list on old patch set', () => {
     const allPatchSets = [{num: 4}, {num: 2}, {num: 1}];
-    assert.equal(element._computePatchInfoClass('1', allPatchSets),
+    assert.equal(element._computePatchInfoClass(1, allPatchSets),
         'patchInfoOldPatchSet');
-    assert.equal(element._computePatchInfoClass('2', allPatchSets),
+    assert.equal(element._computePatchInfoClass(2, allPatchSets),
         'patchInfoOldPatchSet');
-    assert.equal(element._computePatchInfoClass('4', allPatchSets), '');
+    assert.equal(element._computePatchInfoClass(4, allPatchSets), '');
   });
 
   suite('editMode behavior', () => {
diff --git a/polygerrit-ui/app/elements/change/gr-message/gr-message.ts b/polygerrit-ui/app/elements/change/gr-message/gr-message.ts
index fb20f0c..bc61dad 100644
--- a/polygerrit-ui/app/elements/change/gr-message/gr-message.ts
+++ b/polygerrit-ui/app/elements/change/gr-message/gr-message.ts
@@ -46,6 +46,11 @@
 import {appContext} from '../../../services/app-context';
 import {pluralize} from '../../../utils/string-util';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation';
+import {
+  computeAllPatchSets,
+  computeLatestPatchNum,
+  computePredecessor,
+} from '../../../utils/patch-set-util';
 
 const PATCH_SET_PREFIX_PATTERN = /^(?:Uploaded\s*)?(?:P|p)atch (?:S|s)et \d+:\s*(.*)/;
 const LABEL_TITLE_SCORE_PATTERN = /^(-?)([A-Za-z0-9-]+?)([+-]\d+)?[.]?$/;
@@ -270,13 +275,20 @@
   _handleViewPatchsetDiff(e: Event) {
     if (!this.message || !this.change) return;
     const match = this.message.message.match(/Uploaded patch set (\d+)./);
-    if (!match || match.length < 1) return;
-    const patchNum = Number(match[1]);
-    if (isNaN(patchNum)) throw new Error('invalid patchnum in message');
+    let patchNum: PatchSetNum;
+    // Message is of the form "Commit Message was updated" or "Patchset X
+    // was rebased"
+    if (!match || match.length < 1) {
+      patchNum = computeLatestPatchNum(computeAllPatchSets(this.change))!;
+    } else {
+      if (isNaN(Number(match[1])))
+        throw new Error('invalid patchnum in message');
+      patchNum = Number(match[1]) as PatchSetNum;
+    }
     GerritNav.navigateToChange(
       this.change,
-      patchNum as PatchSetNum,
-      (patchNum === 1 ? 'PARENT' : patchNum - 1) as PatchSetNum
+      patchNum,
+      computePredecessor(patchNum)
     );
     // stop propagation to stop message expansion
     e.stopPropagation();
diff --git a/polygerrit-ui/app/elements/change/gr-message/gr-message_test.js b/polygerrit-ui/app/elements/change/gr-message/gr-message_test.js
index 94507e6..facde01 100644
--- a/polygerrit-ui/app/elements/change/gr-message/gr-message_test.js
+++ b/polygerrit-ui/app/elements/change/gr-message/gr-message_test.js
@@ -18,6 +18,7 @@
 import '../../../test/common-test-setup-karma.js';
 import './gr-message.js';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation.js';
+import {createChange, createRevisions} from '../../../test/test-data-generators.js';
 
 const basicFixture = fixtureFromElement('gr-message');
 
@@ -232,7 +233,7 @@
     suite('uploaded patchset X message navigates to X - 1 vs  X', () => {
       let navStub;
       setup(() => {
-        element.change = {changeNum: 12345};
+        element.change = {...createChange(), revisions: createRevisions(4)};
         navStub = sinon.stub(GerritNav, 'navigateToChange');
       });
 
@@ -241,7 +242,7 @@
           message: 'Uploaded patch set 1.',
         };
         element._handleViewPatchsetDiff(new MouseEvent('click'));
-        assert.isTrue(navStub.calledWithExactly({changeNum: 12345}, 1,
+        assert.isTrue(navStub.calledWithExactly(element.change, 1,
             'PARENT'));
       });
 
@@ -250,21 +251,21 @@
           message: 'Uploaded patch set 2.',
         };
         element._handleViewPatchsetDiff(new MouseEvent('click'));
-        assert.isTrue(navStub.calledWithExactly({changeNum: 12345}, 2, 1));
+        assert.isTrue(navStub.calledWithExactly(element.change, 2, 1));
 
         element.message = {
           message: 'Uploaded patch set 200.',
         };
         element._handleViewPatchsetDiff(new MouseEvent('click'));
-        assert.isTrue(navStub.calledWithExactly({changeNum: 12345}, 200, 199));
+        assert.isTrue(navStub.calledWithExactly(element.change, 200, 199));
       });
 
-      test('invalid patchset does not cause navigation', () => {
+      test('Commit message updated', () => {
         element.message = {
-          message: 'Uploaded patch set XYZ.',
+          message: 'Commit message updated.',
         };
         element._handleViewPatchsetDiff(new MouseEvent('click'));
-        assert.isFalse(navStub.called);
+        assert.isTrue(navStub.calledWithExactly(element.change, 4, 3));
       });
     });
 
diff --git a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.ts b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.ts
index fc6b5ba..e6c9f42 100644
--- a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.ts
@@ -25,7 +25,7 @@
 import {htmlTemplate} from './gr-related-changes-list_html';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation';
 import {ChangeStatus} from '../../../constants/constants';
-import {patchNumEquals} from '../../../utils/patch-set-util';
+
 import {changeIsOpen} from '../../../utils/change-util';
 import {getPluginEndpoints} from '../../shared/gr-js-api-interface/gr-plugin-endpoints';
 import {customElement, observe, property} from '@polymer/decorators';
@@ -410,7 +410,7 @@
       return [];
     }
     for (const rev in change.revisions) {
-      if (patchNumEquals(change.revisions[rev]._number, patchNum)) {
+      if (change.revisions[rev]._number === patchNum) {
         changeRevision = rev;
       }
     }
diff --git a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
index 07045cd..2f3d03c 100644
--- a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
+++ b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
@@ -46,10 +46,7 @@
   WeblinkType,
 } from '../gr-navigation/gr-navigation';
 import {appContext} from '../../../services/app-context';
-import {
-  convertToPatchSetNum,
-  patchNumEquals,
-} from '../../../utils/patch-set-util';
+import {convertToPatchSetNum} from '../../../utils/patch-set-util';
 import {customElement, property} from '@polymer/decorators';
 import {assertNever} from '../../../utils/common-util';
 import {
@@ -693,10 +690,7 @@
 
     // Diffing a patch against itself is invalid, so if the base and revision
     // patches are equal clear the base.
-    if (
-      params.patchNum &&
-      patchNumEquals(params.basePatchNum, params.patchNum)
-    ) {
+    if (params.patchNum && params.basePatchNum === params.patchNum) {
       needsRedirect = true;
       params.basePatchNum = null;
     } else if (!hasPatchNum) {
diff --git a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts
index 9988116..5210616 100644
--- a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts
+++ b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts
@@ -18,7 +18,7 @@
 import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
 import {PolymerElement} from '@polymer/polymer/polymer-element';
 import {htmlTemplate} from './gr-comment-api_html';
-import {patchNumEquals, CURRENT} from '../../../utils/patch-set-util';
+import {CURRENT} from '../../../utils/patch-set-util';
 import {customElement, property} from '@polymer/decorators';
 import {
   CommentBasics,
@@ -30,6 +30,7 @@
   NumericChangeId,
   PathToCommentsInfoMap,
   FileInfo,
+  ParentPatchSetNum,
 } from '../../../types/common';
 import {hasOwnProperty} from '../../../utils/common-util';
 import {
@@ -235,9 +236,7 @@
       allComments = allComments.concat(drafts);
     }
     if (patchNum) {
-      allComments = allComments.filter(c =>
-        patchNumEquals(c.patch_set, patchNum)
-      );
+      allComments = allComments.filter(c => c.patch_set === patchNum);
     }
     return allComments.map(c => {
       return {...c};
@@ -284,7 +283,7 @@
   getAllDraftsForPath(path: string, patchNum?: PatchSetNum): Comment[] {
     let comments = this._drafts[path] || [];
     if (patchNum) {
-      comments = comments.filter(c => patchNumEquals(c.patch_set, patchNum));
+      comments = comments.filter(c => c.patch_set === patchNum);
     }
     return comments.map(c => {
       return {...c, __draft: true};
@@ -369,6 +368,10 @@
    * does not return the range of the ported thread and it becomes a file level
    * thread.
    *
+   * If a comment was created with Side=PARENT, then we only show this ported
+   * comment if Base is part of the patch range, always on the left side of
+   * the diff.
+   *
    * @return only the ported threads for the specified file and patch range
    */
   _getPortedCommentThreads(
@@ -407,15 +410,22 @@
         return false;
       }
 
-      // TODO(dhruvsri): Add handling for thread.commentSide = PARENT
-      if (thread.commentSide === CommentSide.PARENT) return false;
+      thread.diffSide = Side.RIGHT;
+      if (thread.commentSide === CommentSide.PARENT) {
+        // TODO(dhruvsri): Add handling for merge parents
+        if (
+          patchRange.basePatchNum !== ParentPatchSetNum ||
+          !!thread.mergeParentNum
+        )
+          return false;
+        thread.diffSide = Side.LEFT;
+      }
 
       if (!isUnresolved(thread) && !isDraftThread(thread)) return false;
 
       thread.range = portedComment.range;
       thread.line = portedComment.line;
       thread.ported = true;
-      thread.diffSide = Side.RIGHT;
       return true;
     });
   }
diff --git a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api_test.js b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api_test.js
index dd36613..e107c16 100644
--- a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api_test.js
+++ b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api_test.js
@@ -20,6 +20,7 @@
 import {ChangeComments} from './gr-comment-api.js';
 import {isInRevisionOfPatchRange, isInBaseOfPatchRange, isDraftThread, isUnresolved, createCommentThreads} from '../../../utils/comment-util.js';
 import {createDraft, createComment, createChangeComments, createCommentThread} from '../../../test/test-data-generators.js';
+import {CommentSide, Side} from '../../../constants/constants.js';
 
 const basicFixture = fixtureFromElement('gr-comment-api');
 
@@ -153,7 +154,7 @@
       const comment1 = {
         ...createComment(),
         unresolved: true,
-        id: 'db977012_e1f13818',
+        id: '1',
         line: 136,
         patch_set: 2,
         range: {
@@ -167,10 +168,22 @@
       const comment2 = {
         ...createComment(),
         patch_set: 2,
-        id: 'ecf0b9fa_fe1a5f62',
+        id: '2',
         line: 5,
       };
 
+      const comment3 = {
+        ...createComment(),
+        side: CommentSide.PARENT,
+        line: 10,
+        unresolved: true,
+      };
+
+      const comment4 = {
+        ...comment3,
+        parent: -2,
+      };
+
       const draft1 = {
         ...createDraft(),
         id: 'db977012_e1f13828',
@@ -277,6 +290,74 @@
         ).length, 0);
       });
 
+      test('comments with side=PARENT are ported over', () => {
+        changeComments = new ChangeComments(
+            {/* comments */
+              // comment left on Base
+              'karma.conf.js': [comment3],
+            },
+            {}/* robot comments */,
+            {/* drafts */
+              'karma.conf.js': [draft2],
+            },
+            {/* ported comments */
+              'karma.conf.js': [{
+                ...comment3,
+                line: 31,
+                patch_set: 4,
+              }],
+            },
+            {}/* ported drafts */
+        );
+
+        const portedThreads = changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: 'PARENT'});
+        assert.equal(portedThreads.length, 1);
+        assert.equal(portedThreads[0].line, 31);
+        assert.equal(portedThreads[0].diffSide, Side.LEFT);
+
+        assert.equal(changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: -2}
+        ).length, 0);
+
+        assert.equal(changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: 2}
+        ).length, 0);
+      });
+
+      test('comments left on merge parent is not ported over', () => {
+        changeComments = new ChangeComments(
+            {/* comments */
+              // comment left on Base
+              'karma.conf.js': [comment4],
+            },
+            {}/* robot comments */,
+            {/* drafts */
+              'karma.conf.js': [draft2],
+            },
+            {/* ported comments */
+              'karma.conf.js': [{
+                ...comment4,
+                line: 31,
+                patch_set: 4,
+              }],
+            },
+            {}/* ported drafts */
+        );
+
+        const portedThreads = changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: 'PARENT'});
+        assert.equal(portedThreads.length, 0);
+
+        assert.equal(changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: -2}
+        ).length, 0);
+
+        assert.equal(changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: 2}
+        ).length, 0);
+      });
+
       test('ported comments contribute to comment count', () => {
         assert.equal(changeComments.computeCommentsString(
             {basePatchNum: 'PARENT', patchNum: 2}, 'karma.conf.js',
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.ts b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.ts
index 601ea80..9574c1d 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.ts
@@ -716,10 +716,19 @@
       }
 
       if (lineNumberEl) {
-        for (const layer of this.layers) {
-          if (typeof layer.annotate === 'function') {
-            layer.annotate(contentText, lineNumberEl, line);
+        const ANNOTATE_MAX_LINE_LENGTH = 1000;
+        // For performance reason, we skip annotating long lines.
+        if (line.text.length < ANNOTATE_MAX_LINE_LENGTH) {
+          for (const layer of this.layers) {
+            if (typeof layer.annotate === 'function') {
+              layer.annotate(contentText, lineNumberEl, line);
+            }
           }
+        } else {
+          const msg =
+            `A line is longer than ${ANNOTATE_MAX_LINE_LENGTH}.` +
+            ' Line annotation was skipped.';
+          console.warn(msg);
         }
       } else {
         console.error('The lineNumberEl is null, skipping layer annotations.');
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
index 2c050f9..d09c811 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
@@ -1040,6 +1040,7 @@
         commentSide: CommentSide.REVISION,
         path: '/p',
         rootId: 'betsys_confession',
+        mergeParentNum: undefined,
         comments: [{
           id: 'betsys_confession',
           path: '/p',
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
index 828c53d..84b227b 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
@@ -44,7 +44,6 @@
 import {
   computeAllPatchSets,
   computeLatestPatchNum,
-  patchNumEquals,
   PatchSet,
 } from '../../../utils/patch-set-util';
 import {
@@ -880,12 +879,10 @@
 
   _displayDiffAgainstLatestToast(latestPatchNum?: PatchSetNum) {
     if (!this._patchRange) return;
-    const leftPatchset = patchNumEquals(
-      this._patchRange.basePatchNum,
-      ParentPatchSetNum
-    )
-      ? 'Base'
-      : `Patchset ${this._patchRange.basePatchNum}`;
+    const leftPatchset =
+      this._patchRange.basePatchNum === ParentPatchSetNum
+        ? 'Base'
+        : `Patchset ${this._patchRange.basePatchNum}`;
     fireAlert(
       this,
       `${leftPatchset} vs
@@ -896,12 +893,12 @@
 
   _displayToasts() {
     if (!this._patchRange) return;
-    if (!patchNumEquals(this._patchRange.basePatchNum, ParentPatchSetNum)) {
+    if (this._patchRange.basePatchNum !== ParentPatchSetNum) {
       this._displayDiffBaseAgainstLeftToast();
       return;
     }
     const latestPatchNum = computeLatestPatchNum(this._allPatchSets);
-    if (!patchNumEquals(this._patchRange.patchNum, latestPatchNum)) {
+    if (this._patchRange.patchNum !== latestPatchNum) {
       this._displayDiffAgainstLatestToast(latestPatchNum);
       return;
     }
@@ -916,17 +913,17 @@
       if (!hasOwnProperty(this._change.revisions, commitSha)) continue;
       const revision = this._change.revisions[commitSha];
       const patchNum = revision._number;
-      if (patchNumEquals(patchNum, this._patchRange.patchNum)) {
+      if (patchNum === this._patchRange.patchNum) {
         commit = commitSha as CommitId;
         const commitObj = revision.commit;
         const parents = commitObj?.parents || [];
         if (
-          patchNumEquals(this._patchRange.basePatchNum, ParentPatchSetNum) &&
+          this._patchRange.basePatchNum === ParentPatchSetNum &&
           parents.length
         ) {
           baseCommit = parents[parents.length - 1].commit;
         }
-      } else if (patchNumEquals(patchNum, this._patchRange.basePatchNum)) {
+      } else if (patchNum === this._patchRange.basePatchNum) {
         baseCommit = commitSha as CommitId;
       }
     }
@@ -1250,7 +1247,7 @@
     if (!patchRange) return {patchNum, basePatchNum};
     if (
       patchRange.basePatchNum !== ParentPatchSetNum ||
-      !patchNumEquals(patchRange.patchNum, latestPatchNum as PatchSetNum)
+      patchRange.patchNum !== latestPatchNum
     ) {
       patchNum = patchRange.patchNum;
       basePatchNum = patchRange.basePatchNum;
@@ -1352,8 +1349,8 @@
 
     const {basePatchNum, patchNum} = e.detail;
     if (
-      patchNumEquals(basePatchNum, this._patchRange.basePatchNum) &&
-      patchNumEquals(patchNum, this._patchRange.patchNum)
+      basePatchNum === this._patchRange.basePatchNum &&
+      patchNum === this._patchRange.patchNum
     ) {
       return;
     }
@@ -1582,7 +1579,7 @@
     patchRangeRecord: PolymerDeepPropertyChange<PatchRange, PatchRange>
   ) {
     const patchRange = patchRangeRecord.base || {};
-    return patchNumEquals(patchRange.patchNum, EditPatchSetNum);
+    return patchRange.patchNum === EditPatchSetNum;
   }
 
   _computeBlameToggleLabel(loaded?: boolean, loading?: boolean) {
@@ -1641,7 +1638,7 @@
     if (!this._path) return;
     if (!this._patchRange) return;
 
-    if (patchNumEquals(this._patchRange.basePatchNum, ParentPatchSetNum)) {
+    if (this._patchRange.basePatchNum === ParentPatchSetNum) {
       fireAlert(this, 'Base is already selected.');
       return;
     }
@@ -1658,7 +1655,7 @@
     if (!this._path) return;
     if (!this._patchRange) return;
 
-    if (patchNumEquals(this._patchRange.basePatchNum, ParentPatchSetNum)) {
+    if (this._patchRange.basePatchNum === ParentPatchSetNum) {
       fireAlert(this, 'Left is already base.');
       return;
     }
@@ -1680,7 +1677,7 @@
     if (!this._patchRange) return;
 
     const latestPatchNum = computeLatestPatchNum(this._allPatchSets);
-    if (patchNumEquals(this._patchRange.patchNum, latestPatchNum)) {
+    if (this._patchRange.patchNum === latestPatchNum) {
       fireAlert(this, 'Latest is already selected.');
       return;
     }
@@ -1700,7 +1697,7 @@
     if (!this._patchRange) return;
 
     const latestPatchNum = computeLatestPatchNum(this._allPatchSets);
-    if (patchNumEquals(this._patchRange.patchNum, latestPatchNum)) {
+    if (this._patchRange.patchNum === latestPatchNum) {
       fireAlert(this, 'Right is already latest.');
       return;
     }
@@ -1720,8 +1717,8 @@
 
     const latestPatchNum = computeLatestPatchNum(this._allPatchSets);
     if (
-      patchNumEquals(this._patchRange.patchNum, latestPatchNum) &&
-      patchNumEquals(this._patchRange.basePatchNum, ParentPatchSetNum)
+      this._patchRange.patchNum === latestPatchNum &&
+      this._patchRange.basePatchNum === ParentPatchSetNum
     ) {
       fireAlert(this, 'Already diffing base against latest.');
       return;
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts
index 04714bb..39d645e 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts
@@ -38,7 +38,7 @@
   rangesEqual,
 } from './gr-diff-utils';
 import {getHiddenScroll} from '../../../scripts/hiddenscroll';
-import {isMergeParent, patchNumEquals} from '../../../utils/patch-set-util';
+import {isMergeParent} from '../../../utils/patch-set-util';
 import {customElement, observe, property} from '@polymer/decorators';
 import {
   BlameInfo,
@@ -605,10 +605,10 @@
       ? this.patchRange.basePatchNum
       : this.patchRange.patchNum;
 
-    const isEdit = patchNumEquals(patchNum, EditPatchSetNum);
+    const isEdit = patchNum === EditPatchSetNum;
     const isEditBase =
-      patchNumEquals(patchNum, ParentPatchSetNum) &&
-      patchNumEquals(this.patchRange.patchNum, EditPatchSetNum);
+      patchNum === ParentPatchSetNum &&
+      this.patchRange.patchNum === EditPatchSetNum;
 
     if (isEdit) {
       fireAlert(this, 'You cannot comment on an edit.');
diff --git a/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.ts b/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.ts
index ec39da2..671bd41 100644
--- a/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.ts
+++ b/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.ts
@@ -30,7 +30,6 @@
   getParentIndex,
   getRevisionByPatchNum,
   isMergeParent,
-  patchNumEquals,
   sortRevisions,
   PatchSet,
 } from '../../../utils/patch-set-util';
@@ -346,7 +345,7 @@
     patchNum: PatchSetNum,
     sortedRevisions: RevisionInfo[]
   ): boolean {
-    if (patchNumEquals(basePatchNum, ParentPatchSetNum)) {
+    if (basePatchNum === ParentPatchSetNum) {
       return false;
     }
 
@@ -441,7 +440,7 @@
       });
       detail.patchNum = patchSetValue;
     } else {
-      if (patchNumEquals(detail.basePatchNum, patchSetValue)) return;
+      if (detail.basePatchNum === patchSetValue) return;
       this.reporting.reportInteraction('left-patchset-changed', {
         previous: detail.basePatchNum,
         current: e.detail.value,
diff --git a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment_html.ts b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment_html.ts
index d9a3187..fbf7f47 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment_html.ts
+++ b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment_html.ts
@@ -264,10 +264,16 @@
           </gr-account-label>
         </template>
         <template is="dom-if" if="[[showPortedComment]]">
-          <a href="[[_getUrlForComment(comment)]]">
-            <span class="portedMessage">
-              Ported from patchset [[comment.patch_set]]
-            </span>
+          <a href="[[_getUrlForComment(comment)]]"
+            ><span class="portedMessage"
+              >Ported from patchset [[comment.patch_set]]</span
+            ></a
+          >
+          <a
+            href="https://bugs.chromium.org/p/gerrit/issues/entry?template=Porting+Comments"
+            target="_blank"
+          >
+            <iron-icon icon="gr-icons:bug" title="report a problem"></iron-icon>
           </a>
         </template>
         <gr-tooltip-content
diff --git a/polygerrit-ui/app/elements/shared/gr-dropdown-list/gr-dropdown-list_html.ts b/polygerrit-ui/app/elements/shared/gr-dropdown-list/gr-dropdown-list_html.ts
index f313174..c163924 100644
--- a/polygerrit-ui/app/elements/shared/gr-dropdown-list/gr-dropdown-list_html.ts
+++ b/polygerrit-ui/app/elements/shared/gr-dropdown-list/gr-dropdown-list_html.ts
@@ -145,7 +145,6 @@
       slot="dropdown-content"
       attr-for-selected="data-value"
       selected="{{value}}"
-      on-tap="_handleDropdownTap"
     >
       <template
         is="dom-repeat"
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface-element.ts b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface-element.ts
index ae6e155..00f9a40 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface-element.ts
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface-element.ts
@@ -18,7 +18,7 @@
 import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
 import {PolymerElement} from '@polymer/polymer/polymer-element';
 import {getPluginLoader} from './gr-plugin-loader';
-import {patchNumEquals} from '../../../utils/patch-set-util';
+
 import {customElement} from '@polymer/decorators';
 import {
   ChangeInfo,
@@ -154,7 +154,7 @@
 
     let revision;
     for (const rev of Object.values(change.revisions || {})) {
-      if (patchNumEquals(rev._number, patchNum)) {
+      if (rev._number === patchNum) {
         revision = rev;
         break;
       }
diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts
index 078e07f..9e77784 100644
--- a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts
+++ b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts
@@ -36,11 +36,7 @@
 import {parseDate} from '../../../utils/date-util';
 import {getBaseUrl} from '../../../utils/url-util';
 import {appContext} from '../../../services/app-context';
-import {
-  getParentIndex,
-  isMergeParent,
-  patchNumEquals,
-} from '../../../utils/patch-set-util';
+import {getParentIndex, isMergeParent} from '../../../utils/patch-set-util';
 import {
   ListChangesOption,
   listChangesOptionsToHex,
@@ -1354,7 +1350,7 @@
     let params = undefined;
     if (isMergeParent(patchRange.basePatchNum)) {
       params = {parent: getParentIndex(patchRange.basePatchNum)};
-    } else if (!patchNumEquals(patchRange.basePatchNum, ParentPatchSetNum)) {
+    } else if (patchRange.basePatchNum !== ParentPatchSetNum) {
       params = {base: patchRange.basePatchNum};
     }
     return this._getChangeURLAndFetch({
@@ -1401,7 +1397,7 @@
     changeNum: NumericChangeId,
     patchRange: PatchRange
   ): Promise<FileNameToFileInfoMap | undefined> {
-    if (patchNumEquals(patchRange.patchNum, EditPatchSetNum)) {
+    if (patchRange.patchNum === EditPatchSetNum) {
       return this.getChangeEditFiles(changeNum, patchRange).then(
         res => res && res.files
       );
@@ -1983,9 +1979,10 @@
       }
       return res;
     };
-    const promise = patchNumEquals(patchNum, EditPatchSetNum)
-      ? this._getFileInChangeEdit(changeNum, path)
-      : this._getFileInRevision(changeNum, path, patchNum, suppress404s);
+    const promise =
+      patchNum === EditPatchSetNum
+        ? this._getFileInChangeEdit(changeNum, path)
+        : this._getFileInRevision(changeNum, path, patchNum, suppress404s);
 
     return promise.then(res => {
       if (!res || !res.ok) {
@@ -2277,8 +2274,7 @@
     };
     if (isMergeParent(basePatchNum)) {
       params.parent = getParentIndex(basePatchNum);
-    } else if (!patchNumEquals(basePatchNum, ParentPatchSetNum)) {
-      // TODO (TS): fix as PatchSetNum in the condition above
+    } else if (basePatchNum !== ParentPatchSetNum) {
       params.base = basePatchNum;
     }
     const endpoint = `/files/${encodeURIComponent(path)}/diff`;
diff --git a/polygerrit-ui/app/elements/shared/revision-info/revision-info.ts b/polygerrit-ui/app/elements/shared/revision-info/revision-info.ts
index fadbfa7..d4bbe16 100644
--- a/polygerrit-ui/app/elements/shared/revision-info/revision-info.ts
+++ b/polygerrit-ui/app/elements/shared/revision-info/revision-info.ts
@@ -15,7 +15,6 @@
  * limitations under the License.
  */
 
-import {patchNumEquals} from '../../../utils/patch-set-util';
 import {ChangeInfo, PatchSetNum} from '../../../types/common';
 import {ParsedChangeInfo} from '../gr-rest-api-interface/gr-reviewer-updates-parser';
 
@@ -71,8 +70,8 @@
 
   getParentId(patchNum: PatchSetNum, parentIndex: number) {
     if (!this.change.revisions) return;
-    const rev = Object.values(this.change.revisions).find(rev =>
-      patchNumEquals(rev._number, patchNum)
+    const rev = Object.values(this.change.revisions).find(
+      rev => rev._number === patchNum
     );
     if (!rev || !rev.commit) return;
     return rev.commit.parents[parentIndex].commit;
diff --git a/polygerrit-ui/app/utils/comment-util.ts b/polygerrit-ui/app/utils/comment-util.ts
index 5d8ea37..f4c0692 100644
--- a/polygerrit-ui/app/utils/comment-util.ts
+++ b/polygerrit-ui/app/utils/comment-util.ts
@@ -29,7 +29,7 @@
 import {parseDate} from './date-util';
 import {LineNumber} from '../elements/diff/gr-diff/gr-diff-line';
 import {CommentIdToCommentThreadMap} from '../elements/diff/gr-comment-api/gr-comment-api';
-import {isMergeParent, getParentIndex, patchNumEquals} from './patch-set-util';
+import {isMergeParent, getParentIndex} from './patch-set-util';
 
 export interface DraftCommentProps {
   __draft?: boolean;
@@ -126,6 +126,7 @@
       comments: [comment],
       patchNum: comment.patch_set,
       commentSide: comment.side ?? CommentSide.REVISION,
+      mergeParentNum: comment.parent,
       path: comment.path,
       line: comment.line,
       range: comment.range,
@@ -151,6 +152,11 @@
   comments: UIComment[];
   path: string;
   commentSide: CommentSide;
+  /* mergeParentNum is the merge parent number only valid for merge commits
+     when commentSide is PARENT.
+     mergeParentNum is undefined for auto merge commits
+  */
+  mergeParentNum?: number;
   patchNum?: PatchSetNum;
   line?: LineNumber;
   /* rootId is optional since we create a empty comment thread element for
@@ -196,7 +202,7 @@
   if (
     range.basePatchNum === ParentPatchSetNum &&
     comment.side === CommentSide.PARENT &&
-    patchNumEquals(comment.patch_set, range.patchNum)
+    comment.patch_set === range.patchNum
   ) {
     return true;
   }
@@ -204,7 +210,7 @@
   return (
     range.basePatchNum !== ParentPatchSetNum &&
     comment.side !== CommentSide.PARENT &&
-    patchNumEquals(comment.patch_set, range.basePatchNum)
+    comment.patch_set === range.basePatchNum
   );
 }
 
@@ -217,8 +223,7 @@
   range: PatchRange
 ) {
   return (
-    comment.side !== CommentSide.PARENT &&
-    patchNumEquals(comment.patch_set, range.patchNum)
+    comment.side !== CommentSide.PARENT && comment.patch_set === range.patchNum
   );
 }
 
@@ -247,7 +252,7 @@
       patchNum: comment.patch_set,
       basePatchNum: ParentPatchSetNum,
     };
-  } else if (patchNumEquals(latestPatchNum, comment.patch_set)) {
+  } else if (latestPatchNum === comment.patch_set) {
     return {
       patchNum: latestPatchNum,
       basePatchNum: ParentPatchSetNum,
diff --git a/polygerrit-ui/app/utils/patch-set-util.ts b/polygerrit-ui/app/utils/patch-set-util.ts
index fda302b..cb0bdec 100644
--- a/polygerrit-ui/app/utils/patch-set-util.ts
+++ b/polygerrit-ui/app/utils/patch-set-util.ts
@@ -60,19 +60,6 @@
 }
 
 /**
- * As patchNum can be either a string (e.g. 'edit', 'PARENT') OR a number,
- * this function checks for patchNum equality.
- *
- */
-export function patchNumEquals(a?: PatchSetNum, b?: PatchSetNum) {
-  if (a === undefined) {
-    return a === b;
-  }
-  // TODO(TS): replace with a===b when the whole code is converted to ts
-  return `${a}` === `${b}`;
-}
-
-/**
  * Whether the given patch is a numbered parent of a merge (i.e. a negative
  * number).
  */
@@ -114,7 +101,7 @@
   patchNum: PatchSetNum
 ) {
   for (const rev of revisions) {
-    if (patchNumEquals(rev._number, patchNum)) {
+    if (rev._number === patchNum) {
       return rev;
     }
   }
@@ -275,6 +262,20 @@
   return allPatchSets[0].num;
 }
 
+export function computePredecessor(
+  patchset?: PatchSetNum
+): PatchSetNum | undefined {
+  if (
+    !patchset ||
+    patchset === ParentPatchSetNum ||
+    patchset === EditPatchSetNum
+  ) {
+    return undefined;
+  }
+  if (patchset === 1) return ParentPatchSetNum;
+  return (Number(patchset) - 1) as PatchSetNum;
+}
+
 export function hasEditBasedOnCurrentPatchSet(allPatchSets: PatchSet[]) {
   if (!allPatchSets || allPatchSets.length < 2) {
     return false;
diff --git a/polygerrit-ui/app/utils/patch-set-util_test.js b/polygerrit-ui/app/utils/patch-set-util_test.js
index 29cc370..12f5ed4 100644
--- a/polygerrit-ui/app/utils/patch-set-util_test.js
+++ b/polygerrit-ui/app/utils/patch-set-util_test.js
@@ -21,7 +21,7 @@
   fetchChangeUpdates, findEditParentPatchNum, findEditParentRevision,
   getParentIndex, getRevisionByPatchNum,
   isMergeParent,
-  patchNumEquals, sortRevisions,
+  sortRevisions,
 } from './patch-set-util.js';
 
 suite('gr-patch-set-util tests', () => {
@@ -31,9 +31,9 @@
       {_number: 1},
       {_number: 2},
     ];
-    assert.deepEqual(getRevisionByPatchNum(revisions, '1'), revisions[1]);
+    assert.deepEqual(getRevisionByPatchNum(revisions, 1), revisions[1]);
     assert.deepEqual(getRevisionByPatchNum(revisions, 2), revisions[2]);
-    assert.equal(getRevisionByPatchNum(revisions, '3'), undefined);
+    assert.equal(getRevisionByPatchNum(revisions, 3), undefined);
   });
 
   test('fetchChangeUpdates on latest', done => {
@@ -231,17 +231,6 @@
         .assertWip(6, true); // PS6 was uploaded with WIP option
   });
 
-  test('patchNumEquals', () => {
-    assert.isFalse(patchNumEquals('edit', 'PARENT'));
-    assert.isFalse(patchNumEquals('edit', NaN));
-    assert.isFalse(patchNumEquals(1, '2'));
-
-    assert.isTrue(patchNumEquals(1, '1'));
-    assert.isTrue(patchNumEquals(1, 1));
-    assert.isTrue(patchNumEquals('edit', 'edit'));
-    assert.isTrue(patchNumEquals('PARENT', 'PARENT'));
-  });
-
   test('isMergeParent', () => {
     assert.isFalse(isMergeParent(1));
     assert.isFalse(isMergeParent(4321));