status: update short status to respect --no-ahead-behind

Teach "git status --short --branch" to respect "--no-ahead-behind"
parameter to skip computing ahead/behind counts for the branch and
its upstream and just report '[different]'.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t6040-tracking-info.sh

@@ -146,6 +146,19 @@ test_expect_success 'status -s -b (diverged from upstream)' '
 	test_i18ncmp expect actual
 '
 
+cat >expect <<\EOF
+## b1...origin/master [different]
+EOF
+
+test_expect_success 'status -s -b --no-ahead-behind (diverged from upstream)' '
+	(
+		cd test &&
+		git checkout b1 >/dev/null &&
+		git status -s -b --no-ahead-behind | head -1
+	) >actual &&
+	test_i18ncmp expect actual
+'
+
 cat >expect <<\EOF
 ## b5...brokenbase [gone]
 EOF

wt-status.c

@@ -1771,7 +1771,7 @@ static void wt_shortstatus_print_tracking(struct wt_status *s)
 	const char *base;
 	char *short_base;
 	const char *branch_name;
-	int num_ours, num_theirs;
+	int num_ours, num_theirs, sti;
 	int upstream_is_gone = 0;
 
 	color_fprintf(s->fp, color(WT_STATUS_HEADER, s), "## ");
@@ -1797,8 +1797,9 @@ static void wt_shortstatus_print_tracking(struct wt_status *s)
 
 	color_fprintf(s->fp, branch_color_local, "%s", branch_name);
 
-	if (stat_tracking_info(branch, &num_ours, &num_theirs, &base,
+	sti = stat_tracking_info(branch, &num_ours, &num_theirs, &base,
-			       AHEAD_BEHIND_FULL) < 0) {
+				 s->ahead_behind_flags);
+	if (sti < 0) {
 		if (!base)
 			goto conclude;
 
@@ -1810,12 +1811,14 @@ static void wt_shortstatus_print_tracking(struct wt_status *s)
 	color_fprintf(s->fp, branch_color_remote, "%s", short_base);
 	free(short_base);
 
-	if (!upstream_is_gone && !num_ours && !num_theirs)
+	if (!upstream_is_gone && !sti)
 		goto conclude;
 
 	color_fprintf(s->fp, header_color, " [");
 	if (upstream_is_gone) {
 		color_fprintf(s->fp, header_color, LABEL(N_("gone")));
+	} else if (s->ahead_behind_flags == AHEAD_BEHIND_QUICK) {
+		color_fprintf(s->fp, header_color, LABEL(N_("different")));
 	} else if (!num_ours) {
 		color_fprintf(s->fp, header_color, LABEL(N_("behind ")));
 		color_fprintf(s->fp, branch_color_remote, "%d", num_theirs);