reflog: convert to parse_options() API

Continue the work started in 33d7bdd645 (builtin/reflog.c: use
parse-options api for expire, delete subcommands, 2022-01-06) and
convert the cmd_reflog() function itself to use the parse_options()
API.

Let's also add a test which would fail if we forgot
PARSE_OPT_NO_INTERNAL_HELP here, as well as making sure that we'll
still pass through "--" by supplying PARSE_OPT_KEEP_DASHDASH. For that
test we need to change "test_commit()" to accept files starting with
"--".

The "git reflog -h" usage will now show the usage for all of the
sub-commands, rather than a terse summary which wasn't
correct (e.g. "git reflog exists" is not a valid command). See my
8757b35d44 (commit-graph: define common usage with a macro,
2021-08-23) for prior art.

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

builtin/reflog.c

@@ -32,6 +32,14 @@ static const char *const reflog_exists_usage[] = {
 	NULL,
 };
 
+static const char *const reflog_usage[] = {
+	N_("git reflog [show] [<log-options>] [<ref>]"),
+	BUILTIN_REFLOG_EXPIRE_USAGE,
+	BUILTIN_REFLOG_DELETE_USAGE,
+	BUILTIN_REFLOG_EXISTS_USAGE,
+	NULL
+};
+
 static timestamp_t default_reflog_expire;
 static timestamp_t default_reflog_expire_unreachable;
 
@@ -372,17 +380,28 @@ static int cmd_reflog_exists(int argc, const char **argv, const char *prefix)
  * main "reflog"
  */
 
-static const char reflog_usage[] =
-"git reflog [ show | expire | delete | exists ]";
-
 int cmd_reflog(int argc, const char **argv, const char *prefix)
 {
-	if (argc > 1 && !strcmp(argv[1], "-h"))
-		usage(_(reflog_usage));
+	struct option options[] = {
+		OPT_END()
+	};
 
-	/* With no command, we default to showing it. */
-	if (argc < 2 || *argv[1] == '-')
-		return cmd_log_reflog(argc, argv, prefix);
+	argc = parse_options(argc, argv, prefix, options, reflog_usage,
+			     PARSE_OPT_KEEP_DASHDASH | PARSE_OPT_KEEP_ARGV0 |
+			     PARSE_OPT_KEEP_UNKNOWN |
+			     PARSE_OPT_NO_INTERNAL_HELP);
+
+	/*
+	 * With "git reflog" we default to showing it. !argc is
+	 * impossible with PARSE_OPT_KEEP_ARGV0.
+	 */
+	if (argc == 1)
+		goto log_reflog;
+
+	if (!strcmp(argv[1], "-h"))
+		usage_with_options(reflog_usage, options);
+	else if (*argv[1] == '-')
+		goto log_reflog;
 
 	if (!strcmp(argv[1], "show"))
 		return cmd_log_reflog(argc - 1, argv + 1, prefix);
@@ -393,5 +412,10 @@ int cmd_reflog(int argc, const char **argv, const char *prefix)
 	else if (!strcmp(argv[1], "exists"))
 		return cmd_reflog_exists(argc - 1, argv + 1, prefix);
 
+	/*
+	 * Fall-through for e.g. "git reflog -1", "git reflog master",
+	 * as well as the plain "git reflog" above goto above.
+	 */
+log_reflog:
 	return cmd_log_reflog(argc, argv, prefix);
 }

t/t1410-reflog.sh

@@ -106,6 +106,23 @@ test_expect_success setup '
 	test_line_count = 4 output
 '
 
+test_expect_success 'correct usage on sub-command -h' '
+	test_expect_code 129 git reflog expire -h >err &&
+	grep "git reflog expire" err
+'
+
+test_expect_success 'pass through -- to sub-command' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	test_commit -C repo message --a-file contents dash-tag &&
+
+	git -C repo reflog show -- --does-not-exist >out &&
+	test_must_be_empty out &&
+	git -C repo reflog show >expect &&
+	git -C repo reflog show -- --a-file >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success rewind '
 	test_tick && git reset --hard HEAD~2 &&
 	test -f C &&

t/test-lib-functions.sh

@@ -329,7 +329,7 @@ test_commit () {
 	else
 		$echo "${3-$1}" >"$indir$file"
 	fi &&
-	git ${indir:+ -C "$indir"} add "$file" &&
+	git ${indir:+ -C "$indir"} add -- "$file" &&
 	if test -z "$notick"
 	then
 		test_tick