new-branch: Add check for branch name before adding

If quickly scanning the command line arguments for the new-release
tool, it may not be obvious that --stable-branch is only needed
one time when initially creating the stable branch, not every time
doing a release off of a stable branch.

This adds a check to make sure the stable branch does not already
exist in the deliverable file before attempting to add the branch
directive for the current release.

Change-Id: Ib15aae2530eb9aebaad23d249dc3d59b022a6d46

openstack_releases/cmds/new_release.py

@@ -244,11 +244,24 @@ def main():
         'version': new_version,
         'projects': projects,
     })
+
     if add_stable_branch:
-        deliverable_info.setdefault('branches', []).append({
+        branch_name = 'stable/{}'.format(series)
-            'name': 'stable/{}'.format(series),
+
-            'location': new_version,
+        # First check if this branch is already defined
-        })
+        if 'branches' in deliverable_info:
+            for branch in deliverable_info['branches']:
+                if branch.get('name') == branch_name:
+                    print('Branch {} already existes, skipping'.format(
+                        branch_name))
+                    add_stable_branch = False
+                    break
+
+        if add_stable_branch:
+            deliverable_info.setdefault('branches', []).append({
+                'name': branch_name,
+                'location': new_version,
+            })
 
     if changes > 0:
         deliverable_filename = 'deliverables/%s/%s.yaml' % (