prune: minor optimization & robustification

If the current project doesn't have any local branches, then there's
nothing to prune, so return right away.  This avoids running a few
git commands when we aren't actually going to use the results, and
it avoids checking repository validity.  Since we aren't going to do
anything in here, no need to check it.

Change-Id: Ie9d5c75a954e42807477299f3e5a63a92fac138b
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/299742
Reviewed-by: Jonathan Nieder <jrn@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/project.py b/project.py
index 45b6c636..bc385f20 100644
--- a/project.py
+++ b/project.py
@@ -1698,6 +1698,11 @@ class Project(object):
         if cb is None or name != cb:
           kill.append(name)
 
+    # Minor optimization: If there's nothing to prune, then don't try to read
+    # any project state.
+    if not kill and not cb:
+      return []
+
     rev = self.GetRevisionId(left)
     if cb is not None \
        and not self._revlist(HEAD + '...' + rev) \