Implement git cl upload -b BUG --bug=BUG.

git_cl.py

Index: git_cl.py
diff --git a/git_cl.py b/git_cl.py
index 7913e989d0345483b70b65e303a711adcf5365fd..831e3d5e1f4b064817f21d81db92bd054fc9f0f1 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -1916,7 +1916,7 @@ class _RietveldChangelistImpl(_ChangelistCodereviewBase):
                                      options.tbr_owners,
                                      change)
       if not options.force:
-        change_desc.prompt()
+        change_desc.prompt(bug=options.bug)
 
       if not change_desc.description:
         print('Description is empty; aborting.')
@@ -2465,7 +2465,7 @@ class _GerritChangelistImpl(_ChangelistCodereviewBase):
           ask_for_data('Press enter to edit now, Ctrl+C to abort')
           if not options.force:
             change_desc = ChangeDescription(message)
-            change_desc.prompt()
+            change_desc.prompt(bug=options.bug)
             message = change_desc.description
             if not message:
               DieWithError("Description is empty. Aborting...")
@@ -2478,7 +2478,7 @@ class _GerritChangelistImpl(_ChangelistCodereviewBase):
         change_desc = ChangeDescription(
             options.message or CreateDescriptionFromLog(args))
         if not options.force:
-          change_desc.prompt()
+          change_desc.prompt(bug=options.bug)
         if not change_desc.description:
           DieWithError("Description is empty. Aborting...")
         message = change_desc.description
@@ -2660,6 +2660,29 @@ def _process_codereview_select_options(parser, options):
     options.forced_codereview = 'rietveld'
 
 
+def _get_bug_line_value(prefix, bugs):
+  """Given prefix and comma separated list of bugs, returns a proper bug line.
+
+  Each bug can be either:
+    * a number, which is combined with prefix
+    * string, which is left as is.
+
+  >>> _get_bug_line_value('v8', '123,chromium:789')
+      'v8:123,chromium:789'

[Sergiy Byelozyorov, 2016/07/01 14:41:12]

I'd also check if each bug is in '\w+:\d+' format. Otherwise, I can write --bug
'foobar' and it will show up as is. Hm, maybe it's a good thing. I will shoot
myself into the foot and will hopefully become smarter... nvm this comment, read
https://xkcd.com/1700/ instead

[tandrii(chromium), 2016/07/01 15:27:04]

Acknowledged.

+  """
+  def to_str(bug):
+    bug = bug.strip()
+    if not prefix:
+      return bug
+    try:
+      return '%s:%d' % (prefix, int(bug))
+    except ValueError:
+      return bug
+    return bug

[Sergiy Byelozyorov, 2016/07/01 14:41:12]

Why is this necessary? You either return inside try or inside exception. Module
quantum bugs, this line should not be reachable.

[tandrii(chromium), 2016/07/01 15:27:04]

yep, leftover.

+  return ','.join(map(to_str, bugs.split(',')))

[Sergiy Byelozyorov, 2016/07/01 14:41:12]

How about ', '.join(...)? Looks nicer for humans, but harder to parse later. I
think Rietveld supports this format. Not sure what Gerrit supports.

[tandrii(chromium), 2016/07/01 15:27:04]

Rietveld doens't care, neither does Gerrit. It's about bugdroid, and after
looking (thanks for making me do so), it actually has this rule:

BUG=proj:1,2 

means proj:1, proj:2. So, I had to cahnge this function to less elegant :(

+
+
+
 class ChangeDescription(object):
   """Contains a parsed form of the change description."""
   R_LINE = r'^[ \t]*(TBR|R)[ \t]*=[ \t]*(.*?)[ \t]*$'
@@ -2735,7 +2758,7 @@ class ChangeDescription(object):
       if new_tbr_line:
         self.append_footer(new_tbr_line)
 
-  def prompt(self):
+  def prompt(self, bug=None):
     """Asks the user to update the description."""
     self.set_description([
       '# Enter a description of the change.',
@@ -2747,7 +2770,10 @@ class ChangeDescription(object):
 
     regexp = re.compile(self.BUG_LINE)
     if not any((regexp.match(line) for line in self._description_lines)):
-      self.append_footer('BUG=%s' % settings.GetBugPrefix())
+      prefix = settings.GetBugPrefix()
+      value = _get_bug_line_value(prefix, bug) if bug else prefix
+      # TODO(tandrii): change this to 'Bug: xxx' to be a proper Gerrit footer.
+      self.append_footer('BUG=%s' % value)
     content = gclient_utils.RunEditor(self.description, True,
                                       git_editor=settings.GetGitEditor())
     if not content:
@@ -3725,6 +3751,9 @@ def CMDupload(parser, args):
   parser.add_option('-f', action='store_true', dest='force',
                     help="force yes to questions (don't prompt)")
   parser.add_option('-m', dest='message', help='message for patchset')
+  parser.add_option('-b', '--bug',
+                    help='pre-populate the bug number(s) for this issue. '
+                         'If several, separate with commas')
   parser.add_option('--message-file', dest='message_file',
                     help='file which contains message for patchset')
   parser.add_option('-t', dest='title',