notes: refactor display notes extra refs field

There's no need to use an extra pointer, which just ends up
leaking memory. The fact that the list is empty tells us the
same thing.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/notes.c b/notes.c
index f6b9b6a..2ec604c 100644
--- a/notes.c
+++ b/notes.c
@@ -1066,9 +1066,9 @@
 
 	git_config(notes_display_config, &load_config_refs);
 
-	if (opt && opt->extra_notes_refs) {
+	if (opt) {
 		struct string_list_item *item;
-		for_each_string_list_item(item, opt->extra_notes_refs)
+		for_each_string_list_item(item, &opt->extra_notes_refs)
 			string_list_add_refs_by_glob(&display_notes_refs,
 						     item->string);
 	}
diff --git a/notes.h b/notes.h
index 60bdf28..7ae3eef 100644
--- a/notes.h
+++ b/notes.h
@@ -1,6 +1,8 @@
 #ifndef NOTES_H
 #define NOTES_H
 
+#include "string-list.h"
+
 /*
  * Function type for combining two notes annotating the same object.
  *
@@ -257,7 +259,7 @@
 
 struct display_notes_opt {
 	unsigned int suppress_default_notes:1;
-	struct string_list *extra_notes_refs;
+	struct string_list extra_notes_refs;
 };
 
 /*
diff --git a/revision.c b/revision.c
index 5826e5d..24b89eb 100644
--- a/revision.c
+++ b/revision.c
@@ -1372,11 +1372,9 @@
 		struct strbuf buf = STRBUF_INIT;
 		revs->show_notes = 1;
 		revs->show_notes_given = 1;
-		if (!revs->notes_opt.extra_notes_refs)
-			revs->notes_opt.extra_notes_refs = xcalloc(1, sizeof(struct string_list));
 		strbuf_addstr(&buf, arg+13);
 		expand_notes_ref(&buf);
-		string_list_append(revs->notes_opt.extra_notes_refs,
+		string_list_append(&revs->notes_opt.extra_notes_refs,
 				   strbuf_detach(&buf, NULL));
 	} else if (!strcmp(arg, "--no-notes")) {
 		revs->show_notes = 0;