Faster branch contains detection for commit

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add specs for Repository#last_commit_for_path

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'faster-branch-contains' into 'master'

Faster branch contains detection for commit

Much faster then iterate over all branches in rugged and look for existing commit

See merge request !1129
Fix download repo featire

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'master' of dev.gitlab.org:gitlab/gitlabhq