Allow using `git cl cherry-pick` in a non-git environment.

This includes:
- adding `--host` parameter to `git-cl cherry-pick`
- adding `GetCommitMessage` to gerrit_util to be able to switch from `git show` used to get the commit message for a change

Bug: b/391547354
Change-Id: I9af227a78af5aaa1bdc98fc2520d98b413f0f3ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6180633
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Gennady Tsitovich <gtsitovich@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

git_cl.py

@@ -4568,13 +4568,9 @@ def _create_commit_message(orig_message, bug=None):
 def CMDcherry_pick(parser, args):
     """Upload a chain of cherry picks to Gerrit.
 
-    This must be run inside the git repo you're trying to make changes to.
+    This should either be run inside the git repo you're trying to make changes
+    to or "--host" should be provided.
     """
-    if gclient_utils.IsEnvCog():
-        print('cherry-pick command is not supported in non-git environment',
-              file=sys.stderr)
-        return 1
-
     parser.add_option('--branch', help='Gerrit branch, e.g. refs/heads/main')
     parser.add_option('--bug',
                       help='Bug to add to the description of each change.')
@@ -4582,16 +4578,36 @@ def CMDcherry_pick(parser, args):
                       type='int',
                       help='The parent change of the first cherry-pick CL, '
                       'i.e. the start of the CL chain.')
+    parser.add_option('--host',
+                      default=None,
+                      help='Gerrit host, needed in case the command is used in '
+                      'a non-git environment.')
     options, args = parser.parse_args(args)
 
+    host = None
+    if options.host:
+        try:
+            host = urllib.parse.urlparse(host).hostname
+        except ValueError as e:
+            print(f'Unable to parse host: {host}. Error: {e}', file=sys.stderr)
+            return 1
+    else:
+        try:
+            host = Changelist().GetGerritHost()
+        except subprocess2.CalledProcessError:
+            pass
+
+    if not host:
+        print('Unable to determine host. cherry-pick command is not supported\n'
+              'in non-git environment without "--host" provided',
+              file=sys.stderr)
+        return 1
+
     if not options.branch:
         parser.error('Branch is required.')
     if not args:
         parser.error('No revisions to cherry pick.')
 
-    # TODO(b/341792235): Consider using GetCommitMessage after b/362567930 is
-    # fixed so this command can be run outside of a git workspace.
-    host = Changelist().GetGerritHost()
     change_ids_to_message = {}
     change_ids_to_commit = {}
 
@@ -4601,16 +4617,20 @@ def CMDcherry_pick(parser, args):
         # unique. Gerrit will error with "Multiple changes found" if we use a
         # non-unique ID. Instead, query Gerrit with the hash and verify it
         # corresponds to a unique CL.
-        changes = gerrit_util.QueryChanges(host, [('commit', commit)])
+        changes = gerrit_util.QueryChanges(
+            host=host,
+            params=[('commit', commit)],
+            o_params=['CURRENT_REVISION', 'CURRENT_COMMIT'],
+        )
         if not changes:
             raise RuntimeError(f'No changes found for {commit}.')
         if len(changes) > 1:
             raise RuntimeError(f'Multiple changes found for {commit}.')
 
-        change_id = changes[0]['id']
+        change = changes[0]
+        change_id = change['id']
+        message = change['revisions'][commit]['commit']['message']
         change_ids_to_commit[change_id] = commit
-
-        message = git_common.run('show', '-s', '--format=%B', commit).strip()
         change_ids_to_message[change_id] = message
 
     print(f'Creating chain of {len(change_ids_to_message)} cherry pick(s)...')