[PATCH 5/7] help: error if [-a|-g|-c] and [-i|-m|-w] are combined

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

Add more sanity checking to "git help" usage by erroring out if these
man viewer options are combined with incompatible command-modes that
will never use these documentation viewers.

This continues the work started in d35d03cf93e (help: simplify by
moving to OPT_CMDMODE(), 2021-09-22) of adding more sanity checking to
"git help". Doing this allows us to clarify the "SYNOPSIS" in the
documentation, and the "git help -h" output.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Documentation/git-help.txt |  2 +-
 builtin/help.c             | 20 ++++++++++++++++++--
 t/t0012-help.sh            | 10 ++++++++++
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-help.txt b/Documentation/git-help.txt
index cf1d53e9499..61d52d30f6c 100644
--- a/Documentation/git-help.txt
+++ b/Documentation/git-help.txt
@@ -9,7 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git help' [-a|--all] [--[no-]verbose]
-	   [[-i|--info] [-m|--man] [-w|--web]] [<command>|<guide>]
+'git help' [[-i|--info] [-m|--man] [-w|--web]] [<command>|<guide>]
 'git help' [-g|--guides]
 'git help' [-c|--config]
 
diff --git a/builtin/help.c b/builtin/help.c
index d387131dd83..125f50f1bb0 100644
--- a/builtin/help.c
+++ b/builtin/help.c
@@ -75,8 +75,8 @@ static struct option builtin_help_options[] = {
 };
 
 static const char * const builtin_help_usage[] = {
-	N_("git help [-a|--all] [--[no-]verbose]]\n"
-	   "         [[-i|--info] [-m|--man] [-w|--web]] [<command>]"),
+	N_("git help [-a|--all] [--[no-]verbose]]"),
+	N_("git help [[-i|--info] [-m|--man] [-w|--web]] [<command>]"),
 	N_("git help [-g|--guides]"),
 	N_("git help [-c|--config]"),
 	NULL
@@ -581,6 +581,13 @@ static void no_extra_argc(int argc)
 			      builtin_help_usage, builtin_help_options);
 }
 
+static void no_format(void)
+{
+	if (help_format != HELP_FORMAT_NONE)
+		usage_msg_opt(_("[-a|--all] cannot be combined with [[-i|--info] [-m|--man] [-w|--web]]"),
+			      builtin_help_usage, builtin_help_options);
+}
+
 int cmd_help(int argc, const char **argv, const char *prefix)
 {
 	int nongit;
@@ -593,6 +600,7 @@ int cmd_help(int argc, const char **argv, const char *prefix)
 
 	switch (cmd_mode) {
 	case HELP_ACTION_ALL:
+		no_format();
 		if (verbose) {
 			setup_pager();
 			list_all_cmds_help();
@@ -605,19 +613,27 @@ int cmd_help(int argc, const char **argv, const char *prefix)
 		break;
 	case HELP_ACTION_GUIDES:
 		no_extra_argc(argc);
+		no_format();
+
 		list_guides_help();
 		printf("%s\n", _(git_more_info_string));
 		return 0;
 	case HELP_ACTION_CONFIG_FOR_COMPLETION:
 		no_extra_argc(argc);
+		no_format();
+
 		list_config_help(SHOW_CONFIG_VARS);
 		return 0;
 	case HELP_ACTION_CONFIG_SECTIONS_FOR_COMPLETION:
 		no_extra_argc(argc);
+		no_format();
+
 		list_config_help(SHOW_CONFIG_SECTIONS);
 		return 0;
 	case HELP_ACTION_CONFIG:
 		no_extra_argc(argc);
+		no_format();
+
 		setup_pager();
 		list_config_help(SHOW_CONFIG_HUMAN);
 		printf("\n%s\n", _("'git help config' for more information"));
diff --git a/t/t0012-help.sh b/t/t0012-help.sh
index 6ac293c19ed..a8c603abd44 100755
--- a/t/t0012-help.sh
+++ b/t/t0012-help.sh
@@ -46,6 +46,16 @@ test_expect_success 'invalid usage' '
 	test_expect_code 129 git help --config-sections-for-completion add
 '
 
+for opt in '-a' '-g' '-c' '--config-for-completion' '--config-sections-for-completion'
+do
+	test_expect_success "invalid usage of '$opt' with [-i|-m|-w]" '
+		git help $opt &&
+		test_expect_code 129 git help $opt -i &&
+		test_expect_code 129 git help $opt -m &&
+		test_expect_code 129 git help $opt -w
+	'
+done
+
 test_expect_success "works for commands and guides by default" '
 	configure_help &&
 	git help status &&
-- 
2.34.1.1257.g2af47340c7b