[PATCH 07/31] refs.c: add a flag to allow reflog updates to truncate the log

[Ronnie Sahlberg <sahlberg@google.com>]

Add a flag that allows us to truncate the reflog before we write the update.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 12 ++++++++++--
 refs.h |  4 +++-
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/refs.c b/refs.c
index d8a1568..a8b583a 100644
--- a/refs.c
+++ b/refs.c
@@ -3608,7 +3608,11 @@ int transaction_commit(struct ref_transaction *transaction,
 		}
 	}
 
-	/* Update all reflog files */
+	/* Update all reflog files
+	   We have already done all ref updates and deletes.
+	   There is not much we can do here if there are any reflog
+	   update errors, other than complain.
+	*/
 	for (i = 0; i < n; i++) {
 		struct ref_update *update = updates[i];
 
@@ -3616,7 +3620,11 @@ int transaction_commit(struct ref_transaction *transaction,
 			continue;
 		if (update->reflog_fd == -1)
 			continue;
-
+		if (update->flags & REFLOG_TRUNCATE)
+			if (lseek(update->reflog_fd, 0, SEEK_SET) < 0 ||
+			    ftruncate(update->reflog_fd, 0)) {
+				error("Could not truncate reflog");
+			}
 		if (log_ref_write_fd(update->reflog_fd, update->old_sha1,
 				     update->new_sha1,
 				     update->committer, update->msg)) {
diff --git a/refs.h b/refs.h
index 2e22a26..b1b97e7 100644
--- a/refs.h
+++ b/refs.h
@@ -269,8 +269,10 @@ int transaction_delete_sha1(struct ref_transaction *transaction,
 			    const unsigned char *old_sha1,
 			    int flags, int have_old, const char *msg);
 
+#define REFLOG_TRUNCATE 0x01
 /*
- * Append a reflog entry for refname.
+ * Append a reflog entry for refname. If the REFLOG_TRUNCATE flag is set
+ * this update will first truncate the reflog before writing the entry.
  */
 int transaction_update_reflog(struct ref_transaction *transaction,
 			      const char *refname,
-- 
2.0.0.rc3.506.g3739a35