If no description is given, use the log messages of all commits for presubmit...

depot_tools/git_cl_hooks.py

 # Copyright (c) 2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import os
 import re
 import subprocess
 import sys
 
 import breakpad
@@ skipping 22 matching lines @@
     self.verbose = None
     self.default_presubmit = None
     self.may_prompt = None
 
     root = Backquote(['git', 'rev-parse', '--show-cdup'])
     if not root:
       root = "."
     absroot = os.path.abspath(root)
     if not root:
       raise Exception("Could not get root directory.")
-    log = Backquote(['git', 'show', '--name-only',
-                     '--pretty=format:%H%n%s%n%n%b'])
-    m = re.match(r'^(\w+)\n(.*)$', log, re.MULTILINE|re.DOTALL)
-    if not m:
-      raise Exception("Could not parse log message: %s" % log)
-    name = m.group(1)
+    # We use the sha1 of HEAD as a name of this change.
+    name = Backquote(['git', 'rev-parse', 'HEAD'])
     files = scm.GIT.CaptureStatus([root], upstream_branch)
     issue = BackquoteAsInteger(['git', 'cl', 'status', '--field=id'])
     patchset = BackquoteAsInteger(['git', 'cl', 'status', '--field=patch'])
     if issue:
       description = Backquote(['git', 'cl', 'status', '--field=desc'])
     else:
-      description = m.group(2)
+      # If the change was never uploaded, use the log messages of all commits
+      # up to the branch point, as git cl upload will prefill the description
+      # with these log messages.
+      description = Backquote(['git', 'log', '--pretty=format:%s%n%n%b',
+                               '%s...' % (upstream_branch)])
     self.change = presubmit_support.GitChange(name, description, absroot, files,
                                               issue, patchset)
 
 
 def RunHooks(hook_name, upstream_branch):
   commit = (hook_name == 'pre-cl-dcommit')
 
   # Create our options based on the command-line args and the current checkout.
   options = ChangeOptions(commit=commit, upstream_branch=upstream_branch)
 
   # Apply watchlists on upload.
   if not commit:
     watchlist = watchlists.Watchlists(options.change.RepositoryRoot())
     files = [f.LocalPath() for f in options.change.AffectedFiles()]
     watchers = watchlist.GetWatchersForPaths(files)
     Backquote(['git', 'config', '--replace-all',
                'rietveld.extracc', ','.join(watchers)])
 
   # Run the presubmit checks.
   if presubmit_support.DoPresubmitChecks(options.change,
                                          options.commit,
                                          options.verbose,
                                          sys.stdout,
                                          sys.stdin,
                                          options.default_presubmit,
                                          options.may_prompt):
     sys.exit(0)
   else:
     sys.exit(1)