[PATCH 4/5] gc: don't run "reflog expire" when keeping reflogs

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Don't redundantly run "git reflog expire --all" when gc.reflogExpire
and gc.reflogExpireUnreachable are set to "never".

I'm being careful to not repeat the issue fixed in
8ab5aa4bd8 ("parseopt: handle malformed --expire arguments more
nicely", 2018-04-21). We'll die early if the config variables are set
to invalid values.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/gc.c  | 17 +++++++++++++++++
 t/t6500-gc.sh | 19 +++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/builtin/gc.c b/builtin/gc.c
index 425d0fa830..91b088dbfe 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -116,6 +116,19 @@ static void process_log_file_on_signal(int signo)
 	raise(signo);
 }
 
+static int gc_config_is_timestamp_never(const char *var)
+{
+	const char *value;
+	timestamp_t expire;
+
+	if (!git_config_get_value(var, &value) && value) {
+		if (parse_expiry_date(value, &expire))
+			die(_("failed to parse '%s' value '%s'"), var, value);
+		return expire == 0;
+	}
+	return 0;
+}
+
 static void gc_config(void)
 {
 	const char *value;
@@ -127,6 +140,10 @@ static void gc_config(void)
 			pack_refs = git_config_bool("gc.packrefs", value);
 	}
 
+	if (gc_config_is_timestamp_never("gc.reflogexpire") &&
+	    gc_config_is_timestamp_never("gc.reflogexpireunreachable"))
+		prune_reflogs = 0;
+
 	git_config_get_int("gc.aggressivewindow", &aggressive_window);
 	git_config_get_int("gc.aggressivedepth", &aggressive_depth);
 	git_config_get_int("gc.auto", &gc_auto_threshold);
diff --git a/t/t6500-gc.sh b/t/t6500-gc.sh
index 4684d06552..7411bf7fec 100755
--- a/t/t6500-gc.sh
+++ b/t/t6500-gc.sh
@@ -120,6 +120,25 @@ test_expect_success 'gc --quiet' '
 	test_must_be_empty stderr
 '
 
+test_expect_success 'gc.reflogExpire{Unreachable,}=never skips "expire" via "gc"' '
+	test_config gc.reflogExpire never &&
+	test_config gc.reflogExpireUnreachable never &&
+
+	GIT_TRACE=$(pwd)/trace.out git gc &&
+
+	# Check that git-pack-refs is run as a sanity check (done via
+	# gc_before_repack()) but that git-expire is not.
+	grep -E "^trace: (built-in|exec|run_command): git pack-refs --" trace.out &&
+	! grep -E "^trace: (built-in|exec|run_command): git reflog expire --" trace.out
+'
+
+test_expect_success 'one of gc.reflogExpire{Unreachable,}=never does not skip "expire" via "gc"' '
+	>trace.out &&
+	test_config gc.reflogExpire never &&
+	GIT_TRACE=$(pwd)/trace.out git gc &&
+	grep -E "^trace: (built-in|exec|run_command): git reflog expire --" trace.out
+'
+
 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
-- 
2.21.0.360.g471c308f928