Use 'Commit message' and 'Merge list' in comment-list

This brings the comment list (both in the messages at the bottom
and in the reply modal dialog) into line with the file list,
emails, and other places the file names are displayed.

Change-Id: Id0ef2e3bafb63070d2284e4b70613ac92300d14d
diff --git a/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.html b/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.html
index 0e640a7..8ad2c19 100644
--- a/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.html
+++ b/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.html
@@ -53,7 +53,9 @@
     </style>
     <template is="dom-repeat" items="[[_computeFilesFromComments(comments)]]" as="file">
       <div class="file">
-        <a href$="[[_computeFileDiffURL(file, changeNum, patchNum)]]">[[file]]</a>:
+        <a href$="[[_computeFileDiffURL(file, changeNum, patchNum)]]">
+          [[_computeFileDisplayName(file)]]
+        </a>:
       </div>
       <template is="dom-repeat"
                 items="[[_computeCommentsForFile(comments, file)]]" as="comment">
diff --git a/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.js b/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.js
index f1fb0fd..98a2508 100644
--- a/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.js
+++ b/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list.js
@@ -14,6 +14,9 @@
 (function() {
   'use strict';
 
+  var COMMIT_MESSAGE_PATH = '/COMMIT_MSG';
+  var MERGE_LIST_PATH = '/MERGE_LIST';
+
   Polymer({
     is: 'gr-comment-list',
 
@@ -39,6 +42,15 @@
         '/' + patchNum + '/' + file;
     },
 
+    _computeFileDisplayName: function(path) {
+      if (path === COMMIT_MESSAGE_PATH) {
+        return 'Commit message';
+      } else if (path === MERGE_LIST_PATH) {
+        return 'Merge list';
+      }
+      return path;
+    },
+
     _isOnParent: function(comment) {
       return comment.side === 'PARENT';
     },
diff --git a/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list_test.html b/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list_test.html
index 34f2951..e27bad0 100644
--- a/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list_test.html
+++ b/polygerrit-ui/app/elements/change/gr-comment-list/gr-comment-list_test.html
@@ -65,6 +65,15 @@
       assert.equal(actual, expected);
     });
 
+    test('_computeFileDisplayName', function() {
+      assert.equal(element._computeFileDisplayName('/COMMIT_MSG'),
+          'Commit message');
+      assert.equal(element._computeFileDisplayName('/MERGE_LIST'),
+          'Merge list');
+      assert.equal(element._computeFileDisplayName('/foo/bar/baz'),
+          '/foo/bar/baz');
+    });
+
     test('_computeDiffLineURL', function() {
       var comment = {line: 123, side: 'REVISION', patch_set: 10};
       var expected = '/c/<change>/<patch>/<file>#123';