[PATCH 1/5] write_ref_to_lockfile(): new function, extracted from write_ref_sha1()

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

This is the first step towards separating the checking and writing of
the new reference value to committing the change.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/refs.c b/refs.c
index 4f495bd..72dae21 100644
--- a/refs.c
+++ b/refs.c
@@ -3017,11 +3017,10 @@ int is_branch(const char *refname)
 }
 
 /*
- * Write sha1 into the ref specified by the lock. Make sure that errno
- * is sane on error.
+ * Write sha1 into the open lockfile, then close the lockfile. On
+ * errors, rollback the lockfile and set errno to reflect the problem.
  */
-static int write_ref_sha1(struct ref_lock *lock,
-	const unsigned char *sha1, const char *logmsg)
+static int write_ref_to_lockfile(struct ref_lock *lock, const unsigned char *sha1)
 {
 	static char term = '\n';
 	struct object *o;
@@ -3050,6 +3049,19 @@ static int write_ref_sha1(struct ref_lock *lock,
 		errno = save_errno;
 		return -1;
 	}
+	return 0;
+}
+
+/*
+ * Write sha1 into the ref specified by the lock. Make sure that errno
+ * is sane on error.
+ */
+static int write_ref_sha1(struct ref_lock *lock,
+	const unsigned char *sha1, const char *logmsg)
+{
+	if (write_ref_to_lockfile(lock, sha1))
+		return -1;
+
 	clear_loose_ref_cache(&ref_cache);
 	if (log_ref_write(lock->ref_name, lock->old_sha1, sha1, logmsg) < 0 ||
 	    (strcmp(lock->ref_name, lock->orig_ref_name) &&
-- 
2.1.4