[PATCH 5/6] help: correct logic error in combining --all and --config

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

Fix a bug in the --config option that's been there ever since its
introduction in 3ac68a93fd2 (help: add --config to list all available
config, 2018-05-26). Die when --all and --config are combined,
combining them doesn't make sense.

The code for the --config option when combined with an earlier
refactoring done to support the --guide option in
65f98358c0c (builtin/help.c: add --guide option, 2013-04-02) would
cause us to take the "--all" branch early and ignore the --config
option.

Let's instead list these as incompatible, both in the synopsis and
help output, and enforce it in the code itself.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Documentation/git-help.txt |  1 +
 builtin/help.c             | 27 ++++++++++++++++++---------
 t/t0012-help.sh            |  5 ++++-
 3 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/Documentation/git-help.txt b/Documentation/git-help.txt
index cb8e3d4da9e..96d5f598b4b 100644
--- a/Documentation/git-help.txt
+++ b/Documentation/git-help.txt
@@ -11,6 +11,7 @@ SYNOPSIS
 'git help' [-a|--all [--[no-]verbose]]
 	   [[-i|--info] [-m|--man] [-w|--web]] [COMMAND|GUIDE]
 'git help' [-g|--guides]
+'git help' [-c|--config]
 
 DESCRIPTION
 -----------
diff --git a/builtin/help.c b/builtin/help.c
index 0737b22069b..83f71d6765e 100644
--- a/builtin/help.c
+++ b/builtin/help.c
@@ -62,6 +62,7 @@ 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 [-g|--guides]"),
+	N_("git help [-c|--config]"),
 	NULL
 };
 
@@ -549,18 +550,26 @@ int cmd_help(int argc, const char **argv, const char *prefix)
 	enum help_format parsed_help_format;
 	const char *page;
 	int standalone = 0;
+	int need_config = 0;
 
 	argc = parse_options(argc, argv, prefix, builtin_help_options,
 			builtin_help_usage, 0);
 	parsed_help_format = help_format;
 
+	/* Incompatible options */
+	if (show_all + !!show_config + show_guides > 1)
+		usage_with_options(builtin_help_usage, builtin_help_options);
+
 	/* Options that take no further arguments */
 	standalone = show_config || show_guides;
 	if (standalone && argc)
 		usage_with_options(builtin_help_usage, builtin_help_options);
 
-	if (show_all) {
+	need_config = show_all || show_config;
+	if (need_config)
 		git_config(git_help_config, NULL);
+
+	if (show_all) {
 		if (verbose) {
 			setup_pager();
 			list_all_cmds_help();
@@ -571,6 +580,14 @@ int cmd_help(int argc, const char **argv, const char *prefix)
 		list_commands(colopts, &main_cmds, &other_cmds);
 	}
 
+	if (show_guides)
+		list_guides_help();
+
+	if (show_all || show_guides) {
+		printf("%s\n", _(git_more_info_string));
+		return 0;
+	}
+
 	if (show_config) {
 		int for_human = show_config == 1;
 
@@ -583,14 +600,6 @@ int cmd_help(int argc, const char **argv, const char *prefix)
 		return 0;
 	}
 
-	if (show_guides)
-		list_guides_help();
-
-	if (show_all || standalone) {
-		printf("%s\n", _(git_more_info_string));
-		return 0;
-	}
-
 	if (!argv[0]) {
 		printf(_("usage: %s%s"), _(git_usage_string), "\n\n");
 		list_common_cmds_help();
diff --git a/t/t0012-help.sh b/t/t0012-help.sh
index 94d1f481c8b..68e7f57470e 100755
--- a/t/t0012-help.sh
+++ b/t/t0012-help.sh
@@ -36,7 +36,10 @@ test_expect_success 'basic help commands' '
 
 test_expect_success 'invalid usage' '
 	test_expect_code 129 git help -c git-add &&
-	test_expect_code 129 git help -g git-add
+	test_expect_code 129 git help -g git-add &&
+
+	test_expect_code 129 git help -a -c &&
+	test_expect_code 129 git help -g -c
 '
 
 test_expect_success "works for commands and guides by default" '
-- 
2.33.0.825.g2bf60429931