show-branch: note about its object flags usage

This is another candidate for commit-slab. Keep Junio's observation in
code so we can search it later on when somebody wants to improve the
code.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/show-branch.c

@@ -22,6 +22,11 @@ static int showbranch_use_color = -1;
 
 static struct argv_array default_args = ARGV_ARRAY_INIT;
 
+/*
+ * TODO: convert this use of commit->object.flags to commit-slab
+ * instead to store a pointer to ref name directly. Then use the same
+ * UNINTERESTING definition from revision.h here.
+ */
 #define UNINTERESTING	01
 
 #define REV_SHIFT	 2

object.h

@@ -43,6 +43,7 @@ struct object_array {
  * builtin/index-pack.c:                                     2021
  * builtin/pack-objects.c:                                   20
  * builtin/reflog.c:                   10--12
+ * builtin/show-branch.c:    0-------------------------------------------26
  * builtin/unpack-objects.c:                                 2021
  */
 #define FLAG_BITS  27