git cl: better detection of messages from CQ.

CQ added support to project-scoped accounts instead of previously
hardcoded commit-bot@ for working with Gerrit.

R=ehmaldonado

Test: `git cl status` on this very CL :)
Bug: 911811
Change-Id: I8f48a7bdc9dad9a5b71d266ccf7e9a493aa94aa9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2095986Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Auto-Submit: Andrii Shyshkalov <tandrii@google.com>

git_cl.py

@@ -102,7 +102,6 @@ TRACES_README_FORMAT = (
 'Execution time: %(execution_time)s\n'
 'Exit code: %(exit_code)s\n') + TRACES_MESSAGE
 
-COMMIT_BOT_EMAIL = 'commit-bot@chromium.org'
 POSTUPSTREAM_HOOK = '.git/hooks/post-cl-land'
 DESCRIPTION_BACKUP_FILE = '.git_cl_description_backup'
 REFS_THAT_ALIAS_TO_OTHER_REFS = {
@@ -1799,13 +1798,12 @@ class Changelist(object):
 
     owner = data['owner'].get('_account_id')
     messages = sorted(data.get('messages', []), key=lambda m: m.get('date'))
-    last_message_author = messages.pop().get('author', {})
-    while last_message_author:
-      if last_message_author.get('email') == COMMIT_BOT_EMAIL:
+    while messages:
+      m = messages.pop()
+      if m.get('tag', '').startswith('autogenerated:cq:'):
         # Ignore replies from CQ.
-        last_message_author = messages.pop().get('author', {})
         continue
-      if last_message_author.get('_account_id') == owner:
+      if m.get('author', {}).get('_account_id') == owner:
         # Most recent message was by owner.
         return 'waiting'
       else:

tests/git_cl_test.py

@@ -2462,8 +2462,8 @@ class TestGitCl(unittest.TestCase):
              u'_revision_number': 1,
              u'author': {
                u'_account_id': 1111084,
-               u'email': u'commit-bot@chromium.org',
-               u'name': u'Commit Bot'
+               u'email': u'could-be-anything@example.com',
+               u'name': u'LUCI CQ'
              },
              u'date': u'2017-03-15 20:08:45.000000000',
              u'id': u'f5a6c25ecbd3b3b54a43ae418ed97eff046dc50b',