clone: fix ref selection in --single-branch --branch=xxx

 - do not fetch HEAD
 - do not also fetch refs following "xxx"
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/clone.c

@@ -433,8 +433,11 @@ static struct ref *wanted_peer_refs(const struct ref *refs,
 
 		if (!option_branch)
 			remote_head = guess_remote_head(head, refs, 0);
-		else
-			remote_head = find_remote_branch(refs, option_branch);
+		else {
+			local_refs = NULL;
+			tail = &local_refs;
+			remote_head = copy_ref(find_remote_branch(refs, option_branch));
+		}
 
 		if (!remote_head && option_branch)
 			warning(_("Could not find remote branch %s to clone."),

t/t5500-fetch-pack.sh

@@ -125,6 +125,11 @@ test_expect_success 'single branch object count' '
 	test_cmp expected count.singlebranch
 '
 
+test_expect_success 'single given branch clone' '
+	git clone --single-branch --branch A "file://$(pwd)/." branch-a &&
+	test_must_fail git --git-dir=branch-a/.git rev-parse origin/B
+'
+
 test_expect_success 'clone shallow' '
 	git clone --no-single-branch --depth 2 "file://$(pwd)/." shallow
 '
@@ -276,7 +281,7 @@ test_expect_success 'clone shallow with --branch' '
 '
 
 test_expect_success 'clone shallow object count' '
-	echo "in-pack: 12" > count3.expected &&
+	echo "in-pack: 6" > count3.expected &&
 	GIT_DIR=shallow3/.git git count-objects -v |
 		grep "^in-pack" > count3.actual &&
 	test_cmp count3.expected count3.actual