trychange.py: create patch refs in refs/patches/

trychange.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Client-side script to send a try job to the try server. It communicates to
 the try server by either writting to a svn/git repository or by directly
 connecting to the server by HTTP.
 """
 
@@ skipping 593 matching lines @@
     if scm.GIT.IsWorkTreeDirty(patch_dir):
       logging.info('Work dir is dirty: hard reset!')
       scm.GIT.Capture(['reset', '--hard'], cwd=patch_dir)
     logging.info('Updating patch repo')
     scm.GIT.Capture(['pull', 'origin', 'master'], cwd=patch_dir)
 
   return os.path.abspath(patch_dir)
 
 
 def _SendChangeGit(bot_spec, options):
-  """Send a change to the try server by committing a diff file to a GIT repo"""
+  """Sends a change to the try server by committing a diff file to a GIT repo.
+
+  Creates a temp orphan branch, commits patch.diff, creates a ref pointing to
+  that commit, deletes the temp branch, checks master out, adds 'ref' file
+  containing the name of the new ref, pushes master and the ref to the origin.
+
+  TODO: instead of creating a temp branch, use git-commit-tree.
+  """
+
   if not options.git_repo:
     raise NoTryServerAccess('Please use the --git_repo option to specify the '
                             'try server git repository to connect to.')
 
   values = _ParseSendChangeOptions(bot_spec, options)
   comment_subject = '%s.%s' % (options.user, options.name)
   comment_body = ''.join("%s=%s\n" % (k, v) for k, v in values)
   description = '%s\n\n%s' % (comment_subject, comment_body)
   logging.info('Sending by GIT')
   logging.info(description)
   logging.info(options.git_repo)
   logging.info(options.diff)
   if options.dry_run:
     return
 
   patch_dir = _GetPatchGitRepo(options.git_repo)
   def patch_git(*args):
     return scm.GIT.Capture(list(args), cwd=patch_dir)
   def add_and_commit(filename, comment_filename):
     patch_git('add', filename)
     patch_git('commit', '-F', comment_filename)
 
   assert scm.GIT.IsInsideWorkTree(patch_dir)
   assert not scm.GIT.IsWorkTreeDirty(patch_dir)
 
   with _PrepareDescriptionAndPatchFiles(description, options) as (
        patch_filename, description_filename):
     logging.info('Committing patch')
-    target_branch = 'refs/patches/%s/%s' % (
+
+    temp_branch = 'tmp_patch'
+    target_ref = 'refs/patches/%s/%s' % (
         Escape(options.user),
         os.path.basename(patch_filename).replace(' ','_'))
     target_filename = os.path.join(patch_dir, 'patch.diff')
     branch_file = os.path.join(patch_dir, GIT_BRANCH_FILE)
+
+    patch_git('checkout', 'master')
     try:
+      # Try deleting an existing temp branch, if any.
+      try:
+        patch_git('branch', '-D', temp_branch)
+        logging.debug('Deleted an existing temp branch.')
+      except subprocess2.CalledProcessError:
+        pass
       # Create a new branch and put the patch there.
-      patch_git('checkout', '--orphan', target_branch)
+      patch_git('checkout', '--orphan', temp_branch)
       patch_git('reset')
       patch_git('clean', '-f')
       shutil.copyfile(patch_filename, target_filename)
       add_and_commit(target_filename, description_filename)
       assert not scm.GIT.IsWorkTreeDirty(patch_dir)
 
-      # Update the branch file in the master
+      # Create a ref and point it to the commit referenced by temp_branch.
+      patch_git('update-ref', target_ref, temp_branch)
+
+      # Delete the temp ref.
       patch_git('checkout', 'master')
+      patch_git('branch', '-D', temp_branch)
 
+      # Update the branch file in the master.
       def update_branch():
         with open(branch_file, 'w') as f:
-          f.write(target_branch)
+          f.write(target_ref)
         add_and_commit(branch_file, description_filename)
 
       update_branch()
 
-      # Push master and target_branch to origin.
+      # Push master and target_ref to origin.
       logging.info('Pushing patch')
       for attempt in xrange(_GIT_PUSH_ATTEMPTS):
         try:
-          patch_git('push', 'origin', 'master', target_branch)
+          patch_git('push', 'origin', 'master', target_ref)
         except subprocess2.CalledProcessError as e:
           is_last = attempt == _GIT_PUSH_ATTEMPTS - 1
           if is_last:
             raise NoTryServerAccess(str(e))
           # Fetch, reset, update branch file again.
           patch_git('fetch', 'origin')
           patch_git('reset', '--hard', 'origin/master')
           update_branch()
     except subprocess2.CalledProcessError, e:
       # Restore state.
@@ skipping 439 matching lines @@
     return 1
   except (gclient_utils.Error, subprocess2.CalledProcessError), e:
     print >> sys.stderr, e
     return 1
   return 0
 
 
 if __name__ == "__main__":
   fix_encoding.fix_encoding()
   sys.exit(TryChange(None, None, False))