[PATCH v3 09/14] refs.c: only write reflog update if msg is non-NULL

[Ronnie Sahlberg <sahlberg@google.com>]

When performing a reflog transaction update, only write to the reflog iff
msg is non-NULL. This can then be combined with REFLOG_TRUNCATE to perform
an update that only truncates but does not write.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 5 +++--
 refs.h | 1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/refs.c b/refs.c
index c33d19e..d6df28d 100644
--- a/refs.c
+++ b/refs.c
@@ -3763,8 +3763,9 @@ int transaction_commit(struct ref_transaction *transaction,
 				update->reflog_fd = -1;
 				continue;
 			}
-		if (log_ref_write_fd(update->reflog_fd, update->old_sha1,
-				     update->new_sha1,
+		if (update->msg &&
+		    log_ref_write_fd(update->reflog_fd,
+				     update->old_sha1, update->new_sha1,
 				     update->committer, update->msg)) {
 			error("Could write to reflog: %s. %s",
 			      update->refname, strerror(errno));
diff --git a/refs.h b/refs.h
index f14c8db..1d7906c 100644
--- a/refs.h
+++ b/refs.h
@@ -337,6 +337,7 @@ int transaction_delete_sha1(struct ref_transaction *transaction,
 /*
  * Append a reflog entry for refname. If the REFLOG_TRUNCATE flag is set
  * this update will first truncate the reflog before writing the entry.
+ * If msg is NULL no update will be written to the log.
  */
 int transaction_update_reflog(struct ref_transaction *transaction,
 			      const char *refname,
-- 
2.0.0.467.g08c0633