morph branch: Fail if branch already exists in the system repo

2 files changed, 13 insertions, 0 deletions

diff --git a/morphlib/git.py b/morphlib/git.py
index 0a4b01f4..f5722ebe 100644
--- a/morphlib/git.py
+++ b/morphlib/git.py
@@ -150,6 +150,14 @@ def checkout_ref(runcmd, gitdir, ref):
     '''Checks out a specific ref/SHA1 in a git working tree.'''
     runcmd(['git', 'checkout', ref], cwd=gitdir)
 
+def ref_exists(runcmd, gitdir, ref):
+    '''Check if specific ref exists locally or in a remote.'''
+    try:
+        runcmd(['git', 'show-ref', '--quiet', ref], cwd=gitdir)
+    except cliapp.AppException:
+        return False
+    return True
+
 def reset_workdir(runcmd, gitdir):
     '''Removes any differences between the current commit '''
     '''and the status of the working directory'''
diff --git a/morphlib/plugins/branch_and_merge_plugin.py b/morphlib/plugins/branch_and_merge_plugin.py
index 714f2838..cb55ade5 100644
--- a/morphlib/plugins/branch_and_merge_plugin.py
+++ b/morphlib/plugins/branch_and_merge_plugin.py
@@ -408,6 +408,11 @@ class BranchAndMergePlugin(cliapp.Plugin):
             repo_dir = os.path.join(branch_dir, self.convert_uri_to_path(repo))
             self.clone_to_directory(repo_dir, repo, commit)
 
+            # Check if branch already exists locally or in a remote
+            if morphlib.git.ref_exists(self.app.runcmd, repo_dir, new_branch):
+                raise cliapp.AppException('branch %s already exists in '
+                                          'repository %s' % (new_branch, repo))
+
             # Create a new branch in the local morphs repository.
             self.app.runcmd(['git', 'checkout', '-b', new_branch, commit],
                             cwd=repo_dir)