--- a/mercurial/repair.py	Wed Nov 02 18:59:29 2016 +0000
+++ b/mercurial/repair.py	Mon Oct 31 15:40:30 2016 -0700
@@ -244,6 +244,9 @@
             vfs.unlink(tmpbundlefile)
 
     repo.destroyed()
+    # return the backup file path (or None if 'backup' was False) so
+    # extensions can use it
+    return backupfile
 
 def rebuildfncache(ui, repo):
     """Rebuilds the fncache file from repo history.