Let --decorate show HEAD position

'git log --graph --oneline --decorate --all' is a useful way to get a
general overview of the repository state, similar to 'gitk --all'.
Let it indicate the position of HEAD by loading that ref too, so that
the --decorate code can see it.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

log-tree.c

@@ -43,6 +43,7 @@ void load_ref_decorations(int flags)
 	if (!loaded) {
 		loaded = 1;
 		for_each_ref(add_ref_decoration, &flags);
+		head_ref(add_ref_decoration, &flags);
 	}
 }