[git-cl] Add cl methods for dealing with git footers.

This is needed for making PostUploadHooks that don't have to re-invent
the git footers library.

Bug:

Change-Id: I0a0ccf3dffd25152c2c273487ddbd9b279d80678
Reviewed-on: https://chromium-review.googlesource.com/461729Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>

git_cl.py

@@ -1402,6 +1402,22 @@ class Changelist(object):
       return '\n'.join([wrapper.fill(line) for line in lines])
     return self.description
 
+  def GetDescriptionFooters(self):
+    """Returns (non_footer_lines, footers) for the commit message.
+
+    Returns:
+      non_footer_lines (list(str)) - Simple list of description lines without
+        any footer. The lines do not contain newlines, nor does the list contain
+        the empty line between the message and the footers.
+      footers (list(tuple(KEY, VALUE))) - List of parsed footers, e.g.
+        [("Change-Id", "Ideadbeef...."), ...]
+    """
+    raw_description = self.GetDescription()
+    msg_lines, _, footers = git_footers.split_footers(raw_description)
+    if footers:
+      msg_lines = msg_lines[:len(msg_lines)-1]
+    return msg_lines, footers
+
   def GetPatchset(self):
     """Returns the patchset number as a int or None if not set."""
     if self.patchset is None and not self.lookedup_patchset:
@@ -1497,6 +1513,29 @@ class Changelist(object):
     self.description = description
     self.has_description = True
 
+  def UpdateDescriptionFooters(self, description_lines, footers, force=False):
+    """Sets the description for this CL remotely.
+
+    You can get description_lines and footers with GetDescriptionFooters.
+
+    Args:
+      description_lines (list(str)) - List of CL description lines without
+        newline characters.
+      footers (list(tuple(KEY, VALUE))) - List of footers, as returned by
+        GetDescriptionFooters. Key must conform to the git footers format (i.e.
+        `List-Of-Tokens`). It will be case-normalized so that each token is
+        title-cased.
+    """
+    new_description = '\n'.join(description_lines)
+    if footers:
+      new_description += '\n'
+      for k, v in footers:
+        foot = '%s: %s' % (git_footers.normalize_name(k), v)
+        if not git_footers.FOOTER_PATTERN.match(foot):
+          raise ValueError('Invalid footer %r' % foot)
+        new_description += foot + '\n'
+    self.UpdateDescription(new_description, force)
+
   def RunHook(self, committing, may_prompt, verbose, change):
     """Calls sys.exit() if the hook fails; returns a HookResults otherwise."""
     try:

tests/git_cl_test.py

@@ -185,6 +185,40 @@ class TestGitClBasic(unittest.TestCase):
     self.assertEquals(cl.GetDescription(force=True), 'y')
     self.assertEquals(cl.GetDescription(), 'y')
 
+  def test_description_footers(self):
+    cl = git_cl.Changelist(issue=1, codereview='gerrit',
+                           codereview_host='host')
+    cl.description = '\n'.join([
+      'This is some message',
+      '',
+      'It has some lines',
+      'and, also',
+      '',
+      'Some: Really',
+      'Awesome: Footers',
+    ])
+    cl.has_description = True
+    cl._codereview_impl.UpdateDescriptionRemote = lambda *a, **kw: 'y'
+    msg, footers = cl.GetDescriptionFooters()
+    self.assertEquals(
+      msg, ['This is some message', '', 'It has some lines', 'and, also'])
+    self.assertEquals(footers, [('Some', 'Really'), ('Awesome', 'Footers')])
+
+    msg.append('wut')
+    footers.append(('gnarly-dude', 'beans'))
+    cl.UpdateDescriptionFooters(msg, footers)
+    self.assertEquals(cl.GetDescription().splitlines(), [
+      'This is some message',
+      '',
+      'It has some lines',
+      'and, also',
+      'wut'
+      '',
+      'Some: Really',
+      'Awesome: Footers',
+      'Gnarly-Dude: beans',
+    ])
+
   def _test_ParseIssueUrl(self, func, url, issue, patchset, hostname, fail):
     parsed = urlparse.urlparse(url)
     result = func(parsed)