Handle branch name kind changes more gracefully.

Scenario: a repository contains a ref: refs/heads/foo and we
          have that in our repository cache.

Action: upstream deletes that ref and then pushes a new refs
        at refs/heads/foo/bar.

Action: we attempt to update the git and the update fails because
        git remote update cannot cope with the 'kind' change of
        refs/heads/foo from ref to directory.

Remedy: If we get an exception from the remote update --prune we
        try the less efficient but more resilient combination of
        first pruning and then updating.

Reviewed-By: Lars Wirzenius (over the shoulder)
Reviewed-By: Richard Maw (over the shoulder)

1 files changed, 5 insertions, 1 deletions

diff --git a/morphlib/cachedrepo.py b/morphlib/cachedrepo.py
index f0ca627b..c40cb657 100644
--- a/morphlib/cachedrepo.py
+++ b/morphlib/cachedrepo.py
@@ -271,7 +271,11 @@ class CachedRepo(object):
             raise CheckoutError(self, ref, target_dir)
 
     def _update(self):  # pragma: no cover
-        self._runcmd(['git', 'remote', 'update', 'origin', '--prune'])
+        try:
+            self._runcmd(['git', 'remote', 'update', 'origin', '--prune'])
+        except cliapp.AppException, ae:
+            self._runcmd(['git', 'remote', 'prune', 'origin'])
+            self._runcmd(['git', 'remote', 'update', 'origin'])
 
     def __str__(self):  # pragma: no cover
         return self.url