Add the ability to get reviewer stats across all stable branches

This adds a special "all" stable branch value handling for the
reviewers entrypoint. This allows one to do something like:

$ reviewers --stable all --days 90 --output ~/stable-all-reviewers-90

It would be nice to be able to specify a specific project, like nova,
with --stable but that is another change for another day.

Change-Id: I045e982e587c9fb2c53a9cb587f944f09c2c5793

README.rst

@@ -34,3 +34,14 @@ object containing the following keys:
 * core-team: A list of Gerrit usernames to consider as core reviewers across
   subprojects.
 * lp_projects: A list of Launchpad project ids to include.
+
+Examples
+--------
+
+#. Get reviewer stats for the last 14 days (default) in the stable/pike branch:
+
+  ``$ reviewers --stable pike --output ~/reviewers-stable-pike-14``
+
+#. Get reviewer stats for the last 90 days across all stable branches:
+
+  ``$ reviewers --stable all --days 90 --output ~/reviewers-stable-all-90``

reviewstats/cmd/reviewers.py

@@ -136,7 +136,11 @@ def write_pretty(reviewer_data, file_obj, options, reviewers, projects,
     else:
         project_name = projects[0]['name']
         if options.stable:
-            project_name = "stable/%s" % (options.stable)
+            # Handle the wildcare case.
+            if options.stable.strip() == 'all':
+                project_name = 'all open stable branches'
+            else:
+                project_name = "stable/%s" % (options.stable)
         file_obj.write(
             'Reviews for the last %d days in %s\n'
             % (options.days, project_name))
@@ -244,7 +248,8 @@ def main(argv=None):
     optparser.add_option(
         '-s', '--stable', default='', metavar='BRANCH',
         help='Generate stats for the specified stable BRANCH ("havana") '
-             'across all integrated projects')
+             'across all integrated projects. Specify "all" for all '
+             'open stable branches.')
     optparser.add_option(
         '-o', '--output', default='-',
         help='Where to write output. If - stdout is used and only one output '

reviewstats/utils.py

@@ -111,7 +111,8 @@ def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
     :param bool only_open: If True, get only the not closed reviews.
     :param str stable:
         Name of the stable branch. If empty string, the changesets are not
-        filtered by any branch.
+        filtered by any branch. The special value "all" is handled to get
+        changes for all open stable branches.
 
     :return: List of de-serialized JSON changeset data as returned by gerrit.
     :rtype: list
@@ -189,7 +190,11 @@ def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
             if only_open:
                 cmd += ' status:open'
             if stable:
-                cmd += ' branch:stable/%s' % stable
+                # Check for "all" to query all stable branches.
+                if stable.strip() == 'all':
+                    cmd += ' branch:^stable/.*'
+                else:
+                    cmd += ' branch:stable/%s' % stable
             if new_count:
                 cmd += ' --start %d' % new_count
             else: