[PATCH] credential: parse subcommands with OPT_SUBCOMMAND

[Wasswa Edson <edsonwasswa54@gmail.com>]

"git credential" dispatches its four subcommands (fill, approve,
reject, capability) with a strcmp() chain after an argc check,
instead of using the parse-options API used by other builtins.

Convert the dispatch to OPT_SUBCOMMAND(). Besides making the code
shorter and more idiomatic, each subcommand gets its own usage
string, so "git credential <subcommand> -h" shows a targeted help
text, and the subcommand names are reported via
--git-completion-helper.

Since the builtin now uses parse-options, drop NO_PARSEOPT from its
git.c entry so "git --list-cmds=parseopt" includes it.

Two pre-existing inconsistencies are fixed while at it:

- The usage string did not mention "capability" even though it is a
  documented subcommand; it now lists all four.
- Documentation/git-credential.adoc marked its SYNOPSIS as a plain
  literal block, which t0450 cannot extract; mark it [verse] and drop
  "credential" from t0450/adoc-help-mismatches.

Behavior changes are limited to error paths: a missing or unknown
subcommand is reported as such ("need a subcommand" / "unknown
subcommand") before the usage text, instead of only showing the
usage text, and "git credential <subcommand> -h" exits 0 after
showing the subcommand's usage. Exit codes for failures are
unchanged (129).

Signed-off-by: Wasswa Edson <edsonwasswa54@gmail.com>
---
 Documentation/git-credential.adoc |   3 +-
 builtin/credential.c              | 148 ++++++++++++++++++++++++------
 git.c                             |   2 +-
 t/t0300-credentials.sh            |  18 ++++
 t/t0450/adoc-help-mismatches      |   1 -
 5 files changed, 138 insertions(+), 34 deletions(-)

diff --git a/Documentation/git-credential.adoc b/Documentation/git-credential.adoc
index e41493292f..e12d429f43 100644
--- a/Documentation/git-credential.adoc
+++ b/Documentation/git-credential.adoc
@@ -7,9 +7,8 @@ git-credential - Retrieve and store user credentials
 
 SYNOPSIS
 --------
-------------------
+[verse]
 'git credential' (fill|approve|reject|capability)
-------------------
 
 DESCRIPTION
 -----------
diff --git a/builtin/credential.c b/builtin/credential.c
index a295c80b36..7b398658bf 100644
--- a/builtin/credential.c
+++ b/builtin/credential.c
@@ -5,48 +5,136 @@
 #include "builtin.h"
 #include "environment.h"
 #include "config.h"
+#include "gettext.h"
+#include "parse-options.h"
 
-static const char usage_msg[] =
-	"git credential (fill|approve|reject)";
+static const char * const credential_usage[] = {
+	N_("git credential (fill|approve|reject|capability)"),
+	NULL,
+};
 
-int cmd_credential(int argc,
-		   const char **argv,
-		   const char *prefix UNUSED,
-		   struct repository *repo UNUSED)
+static const char * const credential_fill_usage[] = {
+	N_("git credential fill"),
+	NULL,
+};
+
+static const char * const credential_approve_usage[] = {
+	N_("git credential approve"),
+	NULL,
+};
+
+static const char * const credential_reject_usage[] = {
+	N_("git credential reject"),
+	NULL,
+};
+
+static const char * const credential_capability_usage[] = {
+	N_("git credential capability"),
+	NULL,
+};
+
+static int cmd_credential_fill(int argc, const char **argv, const char *prefix,
+			       struct repository *repo UNUSED)
 {
-	const char *op;
+	struct option options[] = { OPT_END() };
 	struct credential c = CREDENTIAL_INIT;
 
-	repo_config(the_repository, git_default_config, NULL);
+	argc = parse_options(argc, argv, prefix, options,
+			     credential_fill_usage, 0);
+	if (argc)
+		usage_with_options(credential_fill_usage, options);
+
+	if (credential_read(&c, stdin, CREDENTIAL_OP_INITIAL) < 0)
+		die("unable to read credential from stdin");
+
+	credential_fill(the_repository, &c, 0);
+	credential_next_state(&c);
+	credential_write(&c, stdout, CREDENTIAL_OP_RESPONSE);
+
+	credential_clear(&c);
+	return 0;
+}
 
-	show_usage_if_asked(argc, argv, usage_msg);
-	if (argc != 2)
-		usage(usage_msg);
-	op = argv[1];
+static int cmd_credential_approve(int argc, const char **argv,
+				const char *prefix,
+				struct repository *repo UNUSED)
+{
+	struct option options[] = { OPT_END() };
+	struct credential c = CREDENTIAL_INIT;
 
-	if (!strcmp(op, "capability")) {
-		credential_set_all_capabilities(&c, CREDENTIAL_OP_INITIAL);
-		credential_announce_capabilities(&c, stdout);
-		return 0;
-	}
+	argc = parse_options(argc, argv, prefix, options,
+			     credential_approve_usage, 0);
+	if (argc)
+		usage_with_options(credential_approve_usage, options);
 
 	if (credential_read(&c, stdin, CREDENTIAL_OP_INITIAL) < 0)
 		die("unable to read credential from stdin");
 
-	if (!strcmp(op, "fill")) {
-		credential_fill(the_repository, &c, 0);
-		credential_next_state(&c);
-		credential_write(&c, stdout, CREDENTIAL_OP_RESPONSE);
-	} else if (!strcmp(op, "approve")) {
-		credential_set_all_capabilities(&c, CREDENTIAL_OP_HELPER);
-		credential_approve(the_repository, &c);
-	} else if (!strcmp(op, "reject")) {
-		credential_set_all_capabilities(&c, CREDENTIAL_OP_HELPER);
-		credential_reject(the_repository, &c);
-	} else {
-		usage(usage_msg);
-	}
+	credential_set_all_capabilities(&c, CREDENTIAL_OP_HELPER);
+	credential_approve(the_repository, &c);
 
 	credential_clear(&c);
 	return 0;
 }
+
+static int cmd_credential_reject(int argc, const char **argv,
+				 const char *prefix,
+				 struct repository *repo UNUSED)
+{
+	struct option options[] = { OPT_END() };
+	struct credential c = CREDENTIAL_INIT;
+
+	argc = parse_options(argc, argv, prefix, options,
+			     credential_reject_usage, 0);
+	if (argc)
+		usage_with_options(credential_reject_usage, options);
+
+	if (credential_read(&c, stdin, CREDENTIAL_OP_INITIAL) < 0)
+		die("unable to read credential from stdin");
+
+	credential_set_all_capabilities(&c, CREDENTIAL_OP_HELPER);
+	credential_reject(the_repository, &c);
+
+	credential_clear(&c);
+	return 0;
+}
+
+static int cmd_credential_capability(int argc, const char **argv,
+				     const char *prefix,
+				     struct repository *repo UNUSED)
+{
+	struct option options[] = { OPT_END() };
+	struct credential c = CREDENTIAL_INIT;
+
+	argc = parse_options(argc, argv, prefix, options,
+			     credential_capability_usage, 0);
+	if (argc)
+		usage_with_options(credential_capability_usage, options);
+
+	credential_set_all_capabilities(&c, CREDENTIAL_OP_INITIAL);
+	credential_announce_capabilities(&c, stdout);
+
+	credential_clear(&c);
+	return 0;
+}
+
+int cmd_credential(int argc,
+		   const char **argv,
+		   const char *prefix,
+		   struct repository *repo)
+{
+	parse_opt_subcommand_fn *fn = NULL;
+	struct option options[] = {
+		OPT_SUBCOMMAND("fill", &fn, cmd_credential_fill),
+		OPT_SUBCOMMAND("approve", &fn, cmd_credential_approve),
+		OPT_SUBCOMMAND("reject", &fn, cmd_credential_reject),
+		OPT_SUBCOMMAND("capability", &fn, cmd_credential_capability),
+		OPT_END()
+	};
+
+	repo_config(the_repository, git_default_config, NULL);
+
+	argc = parse_options(argc, argv, prefix, options, credential_usage, 0);
+
+	return fn(argc, argv, prefix, repo);
+}
diff --git a/git.c b/git.c
index d7b5f88e52..da370902ab 100644
--- a/git.c
+++ b/git.c
@@ -562,7 +562,7 @@ static struct cmd_struct commands[] = {
 	{ "commit-tree", cmd_commit_tree, RUN_SETUP },
 	{ "config", cmd_config, RUN_SETUP_GENTLY | DELAY_PAGER_CONFIG },
 	{ "count-objects", cmd_count_objects, RUN_SETUP },
-	{ "credential", cmd_credential, RUN_SETUP_GENTLY | NO_PARSEOPT },
+	{ "credential", cmd_credential, RUN_SETUP_GENTLY },
 	{ "credential-cache", cmd_credential_cache },
 	{ "credential-cache--daemon", cmd_credential_cache_daemon },
 	{ "credential-store", cmd_credential_store },
diff --git a/t/t0300-credentials.sh b/t/t0300-credentials.sh
index ea11cdb4dc..ce230caff1 100755
--- a/t/t0300-credentials.sh
+++ b/t/t0300-credentials.sh
@@ -1056,4 +1056,22 @@ test_expect_success 'interactive prompt is sanitized' '
 	EOF
 '
 
+test_expect_success 'credential subcommands -h show subcommand usage' '
+	for sub in fill approve reject capability
+	do
+		git credential $sub -h >out &&
+		test_grep "^usage: git credential $sub" out || return 1
+	done
+'
+
+test_expect_success 'credential requires a subcommand' '
+	test_expect_code 129 git credential 2>err &&
+	test_grep "need a subcommand" err
+'
+
+test_expect_success 'credential rejects unknown subcommand' '
+	test_expect_code 129 git credential foo 2>err &&
+	test_grep "unknown subcommand" err
+'
+
 test_done
diff --git a/t/t0450/adoc-help-mismatches b/t/t0450/adoc-help-mismatches
index baf3b1d809..939e47bf3a 100644
--- a/t/t0450/adoc-help-mismatches
+++ b/t/t0450/adoc-help-mismatches
@@ -9,7 +9,6 @@ checkout
 checkout-index
 clone
 column
-credential
 credential-cache
 credential-store
 fetch-pack
-- 
2.53.0