Improve gitRef code.
More cleanup and refactoring.
Write remoteRefs whenever fetched.
Fix bug in creating refPaths.
Add support to update remoteRefs in fetch
Update remoteHead async, when requested.
More cleanup.
fix.
Remove old remote refs when updating.
Add api to get update remote branch names.
Merge pull request #2382 from dart-lang/update_gitRefs

Update git refs