Improve abstraction of ref lock/write.

Created 'struct ref_lock' to contain the data necessary to perform
a ref update.  This change improves writing a ref as the file names
are generated only once (rather than twice) and supports following
symrefs (up to the maximum depth).  Further the ref_lock structure
provides room to extend the update API with ref logging.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 16 insertions, 8 deletions

diff --git a/refs.h b/refs.h
index fa816c1e9f..b7e9df2fa9 100644
--- a/refs.h
+++ b/refs.h
@@ -1,6 +1,13 @@
 #ifndef REFS_H
 #define REFS_H
 
+struct ref_lock {
+	char *ref_file;
+	char *lock_file;
+	unsigned char old_sha1[20];
+	int lock_fd;
+};
+
 /*
  * Calls the specified function for each ref file until it returns nonzero,
  * and returns the value
@@ -14,16 +21,17 @@ extern int for_each_remote_ref(int (*fn)(const char *path, const unsigned char *
 /** Reads the refs file specified into sha1 **/
 extern int get_ref_sha1(const char *ref, unsigned char *sha1);
 
-/** Locks ref and returns the fd to give to write_ref_sha1() if the ref
- * has the given value currently; otherwise, returns -1.
- **/
-extern int lock_ref_sha1(const char *ref, const unsigned char *old_sha1);
+/** Locks a "refs/" ref returning the lock on success and NULL on failure. **/
+extern struct ref_lock* lock_ref_sha1(const char *ref, const unsigned char *old_sha1, int mustexist);
+
+/** Locks any ref (for 'HEAD' type refs). */
+extern struct ref_lock* lock_any_ref_for_update(const char *ref, const unsigned char *old_sha1, int mustexist);
 
-/** Writes sha1 into the refs file specified, locked with the given fd. **/
-extern int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1);
+/** Release any lock taken but not written. **/
+extern void unlock_ref (struct ref_lock *lock);
 
-/** Writes sha1 into the refs file specified. **/
-extern int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1);
+/** Writes sha1 into the ref specified by the lock. **/
+extern int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1, const char *msg);
 
 /** Returns 0 if target has the right format for a ref. **/
 extern int check_ref_format(const char *target);