notes: refactor display notes default handling

This is in preparation for more notes-related revision
command-line options.

The "suppress_default_notes" option is renamed to
"use_default_notes", and is now a tri-state with values less
than one indicating "not set".  If the value is "not set",
then we show default refs if and only if no other refs were
given.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

notes.c

@@ -1053,7 +1053,8 @@ void init_display_notes(struct display_notes_opt *opt)
 
 	assert(!display_notes_trees);
 
-	if (!opt || !opt->suppress_default_notes) {
+	if (!opt || opt->use_default_notes > 0 ||
+	    (opt->use_default_notes == -1 && !opt->extra_notes_refs.nr)) {
 		string_list_append(&display_notes_refs, default_notes_ref());
 		display_ref_env = getenv(GIT_NOTES_DISPLAY_REF_ENVIRONMENT);
 		if (display_ref_env) {

notes.h

@@ -258,7 +258,7 @@ void format_note(struct notes_tree *t, const unsigned char *object_sha1,
 struct string_list;
 
 struct display_notes_opt {
-	unsigned int suppress_default_notes:1;
+	int use_default_notes;
 	struct string_list extra_notes_refs;
 };
 

revision.c

@@ -955,6 +955,8 @@ void init_revisions(struct rev_info *revs, const char *prefix)
 		revs->diffopt.prefix = prefix;
 		revs->diffopt.prefix_length = strlen(prefix);
 	}
+
+	revs->notes_opt.use_default_notes = -1;
 }
 
 static void add_pending_commit_list(struct rev_info *revs,
@@ -1368,10 +1370,13 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	} else if (!strcmp(arg, "--show-notes")) {
 		revs->show_notes = 1;
 		revs->show_notes_given = 1;
+		revs->notes_opt.use_default_notes = 1;
 	} else if (!prefixcmp(arg, "--show-notes=")) {
 		struct strbuf buf = STRBUF_INIT;
 		revs->show_notes = 1;
 		revs->show_notes_given = 1;
+		if (revs->notes_opt.use_default_notes < 0)
+			revs->notes_opt.use_default_notes = 1;
 		strbuf_addstr(&buf, arg+13);
 		expand_notes_ref(&buf);
 		string_list_append(&revs->notes_opt.extra_notes_refs,
@@ -1381,9 +1386,9 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->show_notes_given = 1;
 	} else if (!strcmp(arg, "--standard-notes")) {
 		revs->show_notes_given = 1;
-		revs->notes_opt.suppress_default_notes = 0;
+		revs->notes_opt.use_default_notes = 1;
 	} else if (!strcmp(arg, "--no-standard-notes")) {
-		revs->notes_opt.suppress_default_notes = 1;
+		revs->notes_opt.use_default_notes = 0;
 	} else if (!strcmp(arg, "--oneline")) {
 		revs->verbose_header = 1;
 		get_commit_format("oneline", revs);