diff: handle errors gracefully

If `git diff` fails in any project checkout (e.g. an incomplete
sync), make sure we print that error clearly rather than blowing
up, and exit non-zero in the process.

Bug: https://crbug.com/gerrit/11613
Change-Id: I12f278427cced20f23f8047e7e3dba8f442ee25e
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/239236
Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Tested-by: Mike Frysinger <vapier@google.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/subcmds/diff.py b/subcmds/diff.py
index 1f3abd86..fa41e70e 100644
--- a/subcmds/diff.py
+++ b/subcmds/diff.py
@@ -37,5 +37,8 @@ to the Unix 'patch' command.
                  help='Paths are relative to the repository root')
 
   def Execute(self, opt, args):
+    ret = 0
     for project in self.GetProjects(args):
-      project.PrintWorkTreeDiff(opt.absolute)
+      if not project.PrintWorkTreeDiff(opt.absolute):
+        ret = 1
+    return ret