revert: convert resolve_ref() to read_ref_full()

This is the follow up of c689332 (Convert many resolve_ref() calls to
read_ref*() and ref_exists() - 2011-11-13). See the said commit for
rationale.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/revert.c

@@ -901,7 +901,7 @@ static int rollback_single_pick(void)
 	if (!file_exists(git_path("CHERRY_PICK_HEAD")) &&
 	    !file_exists(git_path("REVERT_HEAD")))
 		return error(_("no cherry-pick or revert in progress"));
-	if (!resolve_ref("HEAD", head_sha1, 0, NULL))
+	if (read_ref_full("HEAD", head_sha1, 0, NULL))
 		return error(_("cannot resolve HEAD"));
 	if (is_null_sha1(head_sha1))
 		return error(_("cannot abort from a branch yet to be born"));