sync: Try fetching a tag as a last resort before giving up

If a tagged commit is not reachable by the fetch refspec configured
for the git (usually refs/heads/*) it will not be downloaded by
'git fetch'.  The tag can however be downloaded with 'git fetch
--tags' or 'git fetch tag <tag>'.

This patch fixes the situation when a tag is not found after a
'git fetch'. Repo will issue 'git fetch tag <tag>' before giving
up completely.

Change-Id: I87796a5e1d51fcf398f346a274b7a069df37599a
Signed-off-by: Shawn O. Pearce <sop@google.com>
1 file changed