diff options
authorMichael Haggerty <>2011-09-15 21:10:42 (GMT)
committerJunio C Hamano <>2011-10-05 20:45:31 (GMT)
commit7cb368421f62318f2c0f0e19a83ca34c201aebaa (patch)
parentf989fea0e0b47873de62a355f4766f03a88fb01b (diff)
resolve_ref(): expand documentation
Record information about resolve_ref(), hard-won via reverse engineering, in a comment for future spelunkers. Signed-off-by: Michael Haggerty <> Signed-off-by: Junio C Hamano <>
2 files changed, 33 insertions, 13 deletions
diff --git a/cache.h b/cache.h
index e7bbc0d..2d82f39 100644
--- a/cache.h
+++ b/cache.h
@@ -831,7 +831,39 @@ extern int get_sha1_hex(const char *hex, unsigned char *sha1);
extern char *sha1_to_hex(const unsigned char *sha1); /* static buffer result! */
extern int read_ref(const char *filename, unsigned char *sha1);
-extern const char *resolve_ref(const char *path, unsigned char *sha1, int, int *);
+ * Resolve a reference, recursively following symbolic refererences.
+ *
+ * Store the referred-to object's name in sha1 and return the name of
+ * the non-symbolic reference that ultimately pointed at it. The
+ * return value, if not NULL, is a pointer into either a static buffer
+ * or the input ref.
+ *
+ * If the reference cannot be resolved to an object, the behavior
+ * depends on the "reading" argument:
+ *
+ * - If reading is set, return NULL.
+ *
+ * - If reading is not set, clear sha1 and return the name of the last
+ * reference name in the chain, which will either be a non-symbolic
+ * reference or an undefined reference. If this is a prelude to
+ * "writing" to the ref, the return value is the name of the ref
+ * that will actually be created or changed.
+ *
+ * If flag is non-NULL, set the value that it points to the
+ * combination of REF_ISPACKED (if the reference was found among the
+ * packed references) and REF_ISSYMREF (if the initial reference was a
+ * symbolic reference).
+ *
+ * If ref is not a properly-formatted, normalized reference, return
+ * NULL. If more than MAXDEPTH recursive symbolic lookups are needed,
+ * give up and return NULL.
+ *
+ * errno is sometimes set on errors, but not always.
+ */
+extern const char *resolve_ref(const char *ref, unsigned char *sha1, int reading, int *flag);
extern int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref);
extern int dwim_log(const char *str, int len, unsigned char *sha1, char **ref);
extern int interpret_branch_name(const char *str, struct strbuf *);
diff --git a/refs.c b/refs.c
index 0baa500..096b42c 100644
--- a/refs.c
+++ b/refs.c
@@ -482,18 +482,6 @@ static int get_packed_ref(const char *ref, unsigned char *sha1)
return -1;
- * If the "reading" argument is set, this function finds out what _object_
- * the ref points at by "reading" the ref. The ref, if it is not symbolic,
- * has to exist, and if it is symbolic, it has to point at an existing ref,
- * because the "read" goes through the symref to the ref it points at.
- *
- * The access that is not "reading" may often be "writing", but does not
- * have to; it can be merely checking _where it leads to_. If it is a
- * prelude to "writing" to the ref, a write to a symref that points at
- * yet-to-be-born ref will create the real ref pointed by the symref.
- * reading=0 allows the caller to check where such a symref leads to.
- */
const char *resolve_ref(const char *ref, unsigned char *sha1, int reading, int *flag)
int depth = MAXDEPTH;