Fast-forward a fully merged topic branch during 'repo sync'

Instead of trying to rebase the changes on a topic branch that
has been fully merged into the upstream branch we track, we should
just fast-forward the topic branch to the new upstream revision.
This way the branch doesn't try to rewrite commits that are already
merged in the upstream.

Signed-off-by: Shawn O. Pearce <sop@google.com>
1 file changed