Make sure not to revert local changes.

"git diff --quiet" has a bug ignoring local changes if there's a
unchanged file with a newer timestamp.  This patch works around
the bug.

Change-Id: I0ddc24e0f7af21287c43c1e04dd166ebff6f2dca
Closes-Bug: 1264422
Merge "Make sure not to revert local changes."