commit 1a799d14b71c3f694aa62edf99310bc3e1a482d5
author Dan Willemsen <dwillemsen@google.com> Tue Dec 15 13:40:05 2015 -0800
committer Dan Willemsen <dwillemsen@google.com> Tue Dec 15 14:22:40 2015 -0800
tree de43af900d722c45189dedcd2c30321686af5e77
parent e9becc079c647f6c9477eed83c0aecb2f591fdf4

Fix prune when bare git has detached head

We don't really use HEAD much in the bare git repositories, but there
have been reports of errors in git-symbolic-ref:

  symbolic-ref: fatal: Refusing to point HEAD outside of refs/

That happen when the bare git repo is in the detached head state. It's
possible that previous operations were killed while we were pruning
branches.

Use DetachHead instead of SetHead if we're restoring the repo into a
detached head state.

Change-Id: I9062e8957bc70367d3ded399685ac026fbb421fc

project.py

diff --git a/project.py b/project.py
index 5058088..d54e336 100644
--- a/project.py
+++ b/project.py
@@ -1583,8 +1583,6 @@
 
     if kill:
       old = self.bare_git.GetHead()
-      if old is None:
-        old = 'refs/heads/please_never_use_this_as_a_branch_name'
 
       try:
         self.bare_git.DetachHead(rev)
@@ -1596,7 +1594,10 @@
                        capture_stderr=True)
         b.Wait()
       finally:
-        self.bare_git.SetHead(old)
+        if ID_RE.match(old):
+          self.bare_git.DetachHead(old)
+        else:
+          self.bare_git.SetHead(old)
         left = self._allrefs
 
       for branch in kill: