Merge branch 'ps/transactional-update-ref-stdin'

"git update-ref --stdin" learned a handful of new verbs to let the
user control ref update transactions more explicitly, which helps
as an ingredient to implement two-phase commit-style atomic
ref-updates across multiple repositories.

* ps/transactional-update-ref-stdin:
  update-ref: implement interactive transaction handling
  update-ref: read commands in a line-wise fashion
  update-ref: move transaction handling into `update_refs_stdin()`
  update-ref: pass end pointer instead of strbuf
  update-ref: drop unused argument for `parse_refname`
  update-ref: organize commands in an array
  strbuf: provide function to append whole lines
  git-update-ref.txt: add missing word
  refs: fix segfault when aborting empty transaction

1 files changed, 10 insertions, 8 deletions

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 561c33ac8a..6516c7bc8c 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -2565,16 +2565,18 @@ static void files_transaction_cleanup(struct files_ref_store *refs,
 		}
 	}
 
-	if (backend_data->packed_transaction &&
-	    ref_transaction_abort(backend_data->packed_transaction, &err)) {
-		error("error aborting transaction: %s", err.buf);
-		strbuf_release(&err);
-	}
+	if (backend_data) {
+		if (backend_data->packed_transaction &&
+		    ref_transaction_abort(backend_data->packed_transaction, &err)) {
+			error("error aborting transaction: %s", err.buf);
+			strbuf_release(&err);
+		}
 
-	if (backend_data->packed_refs_locked)
-		packed_refs_unlock(refs->packed_ref_store);
+		if (backend_data->packed_refs_locked)
+			packed_refs_unlock(refs->packed_ref_store);
 
-	free(backend_data);
+		free(backend_data);
+	}
 
 	transaction->state = REF_TRANSACTION_CLOSED;
 }