Add --stop option for bugs-fixed-since

Filter out all the bugs had been merged in stable branch for
a period of time, that is important for downstream team,
so that we can pick some important bugs to backport.

Change-Id: Ib5edd053ac58713e35a6c5818fe2f8fc2d31ba70

README.rst

@@ -773,6 +773,13 @@ Example::
 
   ./bugs-fixed-since.py -r ../neutron --start=8.0.0
 
+Use ``--stop`` option to list bugs mentioned in stable branch messages stopping
+from a specified commit.
+
+Example::
+
+  ./bugs-fixed-since.py -B -r ../neutron --start=8.0.0 --stop=origin/stable/mitaka
+
 Use ``-B`` option to ignore patches that were already backported into all
 stable branches.
 

bugs-fixed-since.py

@@ -38,6 +38,10 @@ def _parse_args():
     parser.add_argument(
         '--start', '-s', required=True,
         help='git hash to start search from')
+    parser.add_argument(
+        '--stop', '-st',
+        help='git hash to stop search to',
+    )
     parser.add_argument(
         '--skip-backported', '-B',
         action='store_true',
@@ -99,7 +103,7 @@ def main():
     # make sure that we work with the latest code
     repo.remotes.origin.fetch()
 
-    latest = repo.refs['origin/master'].commit
+    latest = repo.refs[args.stop if args.stop else 'origin/master'].commit
     rev = '%s..%s' % (args.start, latest.hexsha)
 
     # avoid duplicates