fetch tests: add a test clobbering tag behavior

The test suite only incidentally (and unintentionally) tested for the
current behavior of eager tag clobbering on "fetch". This follow-up to
the previous "push tests: assert re-pushing annotated tags" change
tests for it explicitly.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5516-fetch-push.sh

@@ -1003,6 +1003,30 @@ test_force_push_tag () {
 test_force_push_tag "lightweight tag" "-f"
 test_force_push_tag "annotated tag" "-f -a -m'msg'"
 
+test_force_fetch_tag () {
+	tag_type_description=$1
+	tag_args=$2
+
+	test_expect_success "fetch will clobber an existing $tag_type_description" "
+		mk_test testrepo heads/master &&
+		mk_child testrepo child1 &&
+		mk_child testrepo child2 &&
+		(
+			cd testrepo &&
+			git tag Tag &&
+			git -C ../child1 fetch origin tag Tag &&
+			>file1 &&
+			git add file1 &&
+			git commit -m 'file1' &&
+			git tag $tag_args Tag &&
+			git -C ../child1 fetch origin tag Tag
+		)
+	"
+}
+
+test_force_fetch_tag "lightweight tag" "-f"
+test_force_fetch_tag "annotated tag" "-f -a -m'msg'"
+
 test_expect_success 'push --porcelain' '
 	mk_empty testrepo &&
 	echo >.git/foo  "To testrepo" &&