notes: extract logic into set_display_notes()

Instead of open coding the logic that tweaks the variables in
`struct display_notes_opt` within handle_revision_opt(), abstract away the
logic into set_display_notes() so that it can be reused.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

notes.c

@@ -1045,6 +1045,30 @@ void init_display_notes(struct display_notes_opt *opt)
 	opt->use_default_notes = -1;
 }
 
+int set_display_notes(struct display_notes_opt *opt, int show_notes, const char *opt_ref)
+{
+	if (show_notes) {
+		if (opt_ref) {
+			struct strbuf buf = STRBUF_INIT;
+			strbuf_addstr(&buf, opt_ref);
+			expand_notes_ref(&buf);
+			string_list_append(&opt->extra_notes_refs,
+					   strbuf_detach(&buf, NULL));
+		} else {
+			opt->use_default_notes = 1;
+		}
+	} else {
+		opt->use_default_notes = -1;
+		/* we have been strdup'ing ourselves, so trick
+		 * string_list into free()ing strings */
+		opt->extra_notes_refs.strdup_strings = 1;
+		string_list_clear(&opt->extra_notes_refs, 0);
+		opt->extra_notes_refs.strdup_strings = 0;
+	}
+
+	return !!show_notes;
+}
+
 void load_display_notes(struct display_notes_opt *opt)
 {
 	char *display_ref_env;

notes.h

@@ -265,6 +265,16 @@ struct display_notes_opt {
  */
 void init_display_notes(struct display_notes_opt *opt);
 
+/*
+ * Set a display_notes_opt to a given state. 'show_notes' is a boolean
+ * representing whether or not to show notes. 'opt_ref' points to a
+ * string for the notes ref, or is NULL if the default notes should be
+ * used.
+ *
+ * Return 'show_notes' normalized to 1 or 0.
+ */
+int set_display_notes(struct display_notes_opt *opt, int show_notes, const char *opt_ref);
+
 /*
  * Load the notes machinery for displaying several notes trees.
  *

revision.c

@@ -2172,9 +2172,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 			die("'%s': not a non-negative integer", arg);
 		revs->expand_tabs_in_log = val;
 	} else if (!strcmp(arg, "--show-notes") || !strcmp(arg, "--notes")) {
-		revs->show_notes = 1;
+		revs->show_notes = set_display_notes(&revs->notes_opt, 1, NULL);
 		revs->show_notes_given = 1;
-		revs->notes_opt.use_default_notes = 1;
 	} else if (!strcmp(arg, "--show-signature")) {
 		revs->show_signature = 1;
 	} else if (!strcmp(arg, "--no-show-signature")) {
@@ -2189,25 +2188,14 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->track_first_time = 1;
 	} else if (skip_prefix(arg, "--show-notes=", &optarg) ||
 		   skip_prefix(arg, "--notes=", &optarg)) {
-		struct strbuf buf = STRBUF_INIT;
-		revs->show_notes = 1;
-		revs->show_notes_given = 1;
 		if (starts_with(arg, "--show-notes=") &&
 		    revs->notes_opt.use_default_notes < 0)
 			revs->notes_opt.use_default_notes = 1;
-		strbuf_addstr(&buf, optarg);
-		expand_notes_ref(&buf);
-		string_list_append(&revs->notes_opt.extra_notes_refs,
-				   strbuf_detach(&buf, NULL));
+		revs->show_notes = set_display_notes(&revs->notes_opt, 1, optarg);
+		revs->show_notes_given = 1;
 	} else if (!strcmp(arg, "--no-notes")) {
-		revs->show_notes = 0;
+		revs->show_notes = set_display_notes(&revs->notes_opt, 0, NULL);
 		revs->show_notes_given = 1;
-		revs->notes_opt.use_default_notes = -1;
-		/* we have been strdup'ing ourselves, so trick
-		 * string_list into free()ing strings */
-		revs->notes_opt.extra_notes_refs.strdup_strings = 1;
-		string_list_clear(&revs->notes_opt.extra_notes_refs, 0);
-		revs->notes_opt.extra_notes_refs.strdup_strings = 0;
 	} else if (!strcmp(arg, "--standard-notes")) {
 		revs->show_notes_given = 1;
 		revs->notes_opt.use_default_notes = 1;