[PATCH v2 22/33] refs: allow log-only updates

[Michael Haggerty <mhagger@alum.mit.edu>]

From: David Turner <dturner@twopensource.com>

The refs infrastructure learns about log-only ref updates, which only
update the reflog.  Later, we will use this to separate symbolic
reference resolution from ref updating.

Signed-off-by: David Turner <dturner@twopensource.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs/files-backend.c | 16 ++++++++++------
 refs/refs-internal.h |  7 +++++++
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/refs/files-backend.c b/refs/files-backend.c
index f4f7953..3f546d0 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -2683,7 +2683,7 @@ static int commit_ref_update(struct ref_lock *lock,
 			}
 		}
 	}
-	if (commit_ref(lock)) {
+	if (!(flags & REF_LOG_ONLY) && commit_ref(lock)) {
 		strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
 		unlock_ref(lock);
 		return -1;
@@ -3101,7 +3101,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 			goto cleanup;
 		}
 		if ((update->flags & REF_HAVE_NEW) &&
-		    !(update->flags & REF_DELETING)) {
+		    !(update->flags & REF_DELETING) &&
+		    !(update->flags & REF_LOG_ONLY)) {
 			int overwriting_symref = ((update->type & REF_ISSYMREF) &&
 						  (update->flags & REF_NODEREF));
 
@@ -3133,8 +3134,9 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 		}
 		if (!(update->flags & REF_NEEDS_COMMIT)) {
 			/*
-			 * We didn't have to write anything to the lockfile.
-			 * Close it to free up the file descriptor:
+			 * We didn't call write_ref_to_lockfile(), so
+			 * the lockfile is still open. Close it to
+			 * free up the file descriptor:
 			 */
 			if (close_ref(update->lock)) {
 				strbuf_addf(err, "couldn't close '%s.lock'",
@@ -3149,7 +3151,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 	for (i = 0; i < transaction->nr; i++) {
 		struct ref_update *update = updates[i];
 
-		if (update->flags & REF_NEEDS_COMMIT) {
+		if (update->flags & REF_NEEDS_COMMIT ||
+		    update->flags & REF_LOG_ONLY) {
 			if (commit_ref_update(update->lock,
 					      update->new_sha1, update->msg,
 					      update->flags, err)) {
@@ -3168,7 +3171,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 	for (i = 0; i < transaction->nr; i++) {
 		struct ref_update *update = updates[i];
 
-		if (update->flags & REF_DELETING) {
+		if (update->flags & REF_DELETING &&
+		    !(update->flags & REF_LOG_ONLY)) {
 			if (delete_ref_loose(update->lock, update->type, err)) {
 				ret = TRANSACTION_GENERIC_ERROR;
 				goto cleanup;
diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 1f94f7a..85f4650 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -43,6 +43,13 @@
  */
 
 /*
+ * Used as a flag in ref_update::flags when we want to log a ref
+ * update but not actually perform it.  This is used when a symbolic
+ * ref update is split up.
+ */
+#define REF_LOG_ONLY 0x80
+
+/*
  * Return true iff refname is minimally safe. "Safe" here means that
  * deleting a loose reference by this name will not do any damage, for
  * example by causing a file that is not a reference to be deleted.
-- 
2.8.1