Merge branch 'kn/fetch-push-bulk-ref-update'

"git push" and "git fetch" are taught to update refs in batches to gain performance. * kn/fetch-push-bulk-ref-update: receive-pack: handle reference deletions separately refs/files: skip updates with errors in batched updates receive-pack: use batched reference updates send-pack: fix memory leak around duplicate refs fetch: use batched reference updates refs: add function to translate errors to strings