Merge branch 'kn/non-transactional-batch-updates'

Updating multiple references have only been possible in all-or-none fashion with transactions, but it can be more efficient to batch multiple updates even when some of them are allowed to fail in a best-effort manner. A new "best effort batches of updates" mode has been introduced. * kn/non-transactional-batch-updates: update-ref: add --batch-updates flag for stdin mode refs: support rejection in batch updates during F/D checks refs: implement batch reference update support refs: introduce enum-based transaction error types refs/reftable: extract code from the transaction preparation refs/files: remove duplicate duplicates check refs: move duplicate refname update check to generic layer refs/files: remove redundant check in split_symref_update()