gc: fix regression in 7b0f229222 impacting --quiet

Fix a regression in my recent 7b0f229222 ("commit-graph write: add
progress output", 2018-09-17).  The newly added progress output for
"commit-graph write" didn't check the --quiet option.

Do so, and add a test asserting that this works as expected. Since the
TTY prequisite isn't available everywhere let's add a version of this
that both requires and doesn't require that. This test might be overly
specific and will break if new progress output is added, but I think
it'll serve as a good reminder to test the undertested progress
mode(s).

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

builtin/gc.c

@@ -647,7 +647,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 
 	if (gc_write_commit_graph)
 		write_commit_graph_reachable(get_object_directory(), 0,
-					     !daemonized);
+					     !quiet && !daemonized);
 
 	if (auto_gc && too_many_loose_objects())
 		warning(_("There are too many unreachable loose objects; "

t/t6500-gc.sh

@@ -4,6 +4,7 @@ test_description='basic git gc tests
 '
 
 . ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-terminal.sh
 
 test_expect_success 'setup' '
 	# do not let the amount of physical memory affects gc
@@ -99,6 +100,26 @@ test_expect_success 'auto gc with too many loose objects does not attempt to cre
 	test_line_count = 2 new # There is one new pack and its .idx
 '
 
+test_expect_success 'gc --no-quiet' '
+	git -c gc.writeCommitGraph=true gc --no-quiet >stdout 2>stderr &&
+	test_must_be_empty stdout &&
+	test_line_count = 1 stderr &&
+	test_i18ngrep "Computing commit graph generation numbers" stderr
+'
+
+test_expect_success TTY 'with TTY: gc --no-quiet' '
+	test_terminal git -c gc.writeCommitGraph=true gc --no-quiet >stdout 2>stderr &&
+	test_must_be_empty stdout &&
+	test_i18ngrep "Enumerating objects" stderr &&
+	test_i18ngrep "Computing commit graph generation numbers" stderr
+'
+
+test_expect_success 'gc --quiet' '
+	git -c gc.writeCommitGraph=true gc --quiet >stdout 2>stderr &&
+	test_must_be_empty stdout &&
+	test_must_be_empty stderr
+'
+
 run_and_wait_for_auto_gc () {
 	# We read stdout from gc for the side effect of waiting until the
 	# background gc process exits, closing its fd 9.  Furthermore, the