refs: pass refname when invoking reflog entry callback

With `refs_for_each_reflog_ent()` callers can iterate through all the
reflog entries for a given reference. The callback that is being invoked
for each such entry does not receive the name of the reference that we
are currently iterating through. This isn't really a limiting factor, as
callers can simply pass the name via the callback data.

But this layout sometimes does make for a bit of an awkward calling
pattern. One example: when iterating through all reflogs, and for each
reflog we iterate through all refnames, we have to do some extra book
keeping to track which reference name we are currently yielding reflog
entries for.

Change the signature of the callback function so that the reference name
of the reflog gets passed through to it. Adapt callers accordingly and
start using the new parameter in trivial cases. The next commit will
refactor the reference migration logic to make use of this parameter so
that we can simplify its logic a bit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.h

@@ -558,10 +558,13 @@ int refs_delete_reflog(struct ref_store *refs, const char *refname);
  * The cb_data is a caller-supplied pointer given to the iterator
  * functions.
  */
-typedef int each_reflog_ent_fn(
-		struct object_id *old_oid, struct object_id *new_oid,
-		const char *committer, timestamp_t timestamp,
-		int tz, const char *msg, void *cb_data);
+typedef int each_reflog_ent_fn(const char *refname,
+			       struct object_id *old_oid,
+			       struct object_id *new_oid,
+			       const char *committer,
+			       timestamp_t timestamp,
+			       int tz, const char *msg,
+			       void *cb_data);
 
 /* Iterate over reflog entries in the log for `refname`. */