help: add --no-[external-commands|aliases] for use with --all

Add the ability to only emit git's own usage information under
--all. This also allows us to extend the "test_section_spacing" tests
added in a preceding commit to test "git help --all"
output.

Previously we could not do that, as the tests might find a git-*
command in the "$PATH", which would make the output differ from one
setup to another.

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

Documentation/git-help.txt

@@ -8,7 +8,7 @@ git-help - Display help information about Git
 SYNOPSIS
 --------
 [verse]
-'git help' [-a|--all] [--[no-]verbose]
+'git help' [-a|--all] [--[no-]verbose] [--[no-]external-commands] [--[no-]aliases]
 'git help' [[-i|--info] [-m|--man] [-w|--web]] [<command>|<guide>]
 'git help' [-g|--guides]
 'git help' [-c|--config]
@@ -48,6 +48,14 @@ OPTIONS
 --all::
 	Prints all the available commands on the standard output.
 
+--no-external-commands::
+	When used with `--all`, exclude the listing of external "git-*"
+	commands found in the `$PATH`.
+
+--no-aliases::
+	When used with `--all`, exclude the listing of configured
+	aliases.
+
 --verbose::
 	When used with `--all` print description for all recognized
 	commands. This is the default.

builtin/help.c

@@ -51,9 +51,14 @@ static const char *html_path;
 static int verbose = 1;
 static enum help_format help_format = HELP_FORMAT_NONE;
 static int exclude_guides;
+static int show_external_commands = -1;
+static int show_aliases = -1;
 static struct option builtin_help_options[] = {
 	OPT_CMDMODE('a', "all", &cmd_mode, N_("print all available commands"),
 		    HELP_ACTION_ALL),
+	OPT_BOOL(0, "external-commands", &show_external_commands,
+		 N_("show external commands in --all")),
+	OPT_BOOL(0, "aliases", &show_aliases, N_("show aliases in --all")),
 	OPT_HIDDEN_BOOL(0, "exclude-guides", &exclude_guides, N_("exclude guides")),
 	OPT_SET_INT('m', "man", &help_format, N_("show man page"), HELP_FORMAT_MAN),
 	OPT_SET_INT('w', "web", &help_format, N_("show manual in web browser"),
@@ -75,7 +80,7 @@ static struct option builtin_help_options[] = {
 };
 
 static const char * const builtin_help_usage[] = {
-	N_("git help [-a|--all] [--[no-]verbose]]"),
+	N_("git help [-a|--all] [--[no-]verbose]] [--[no-]external-commands] [--[no-]aliases]"),
 	N_("git help [[-i|--info] [-m|--man] [-w|--web]] [<command>]"),
 	N_("git help [-g|--guides]"),
 	N_("git help [-c|--config]"),
@@ -620,12 +625,19 @@ int cmd_help(int argc, const char **argv, const char *prefix)
 			builtin_help_usage, 0);
 	parsed_help_format = help_format;
 
+	if (cmd_mode != HELP_ACTION_ALL &&
+	    (show_external_commands >= 0 ||
+	     show_aliases >= 0))
+		usage_msg_opt(_("the '--no-[external-commands|aliases]' options can only be used with '--all'"),
+			      builtin_help_usage, builtin_help_options);
+
 	switch (cmd_mode) {
 	case HELP_ACTION_ALL:
 		opt_mode_usage(argc, "--all", help_format);
 		if (verbose) {
 			setup_pager();
-			list_all_cmds_help();
+			list_all_cmds_help(show_external_commands,
+					   show_aliases);
 			return 0;
 		}
 		printf(_("usage: %s%s"), _(git_usage_string), "\n\n");

help.c

@@ -476,15 +476,17 @@ static void list_all_cmds_help_aliases(int longest)
 	string_list_clear(&alias_list, 1);
 }
 
-void list_all_cmds_help(void)
+void list_all_cmds_help(int show_external_commands, int show_aliases)
 {
 	int longest;
 
 	puts(_("See 'git help <command>' to read about a specific subcommand"));
 	print_cmd_by_category(main_categories, &longest);
 
-	list_all_cmds_help_external_commands();
-	list_all_cmds_help_aliases(longest);
+	if (show_external_commands)
+		list_all_cmds_help_external_commands();
+	if (show_aliases)
+		list_all_cmds_help_aliases(longest);
 }
 
 int is_in_cmdlist(struct cmdnames *c, const char *s)

help.h

@@ -20,7 +20,7 @@ static inline void mput_char(char c, unsigned int num)
 }
 
 void list_common_cmds_help(void);
-void list_all_cmds_help(void);
+void list_all_cmds_help(int show_external_commands, int show_aliases);
 void list_guides_help(void);
 
 void list_all_main_cmds(struct string_list *list);

t/t0012-help.sh

@@ -57,6 +57,19 @@ do
 		test_expect_code 129 git help $opt -m &&
 		test_expect_code 129 git help $opt -w
 	'
+
+	if test "$opt" = "-a"
+	then
+		continue
+	fi
+
+	test_expect_success "invalid usage of '$opt' with --no-external-commands" '
+		test_expect_code 129 git help $opt --no-external-commands
+	'
+
+	test_expect_success "invalid usage of '$opt' with --no-aliases" '
+		test_expect_code 129 git help $opt --no-external-commands
+	'
 done
 
 test_expect_success "works for commands and guides by default" '
@@ -187,6 +200,30 @@ do
 	'
 done
 
+test_expect_success "'git help -a' section spacing" '
+	test_section_spacing \
+		git help -a --no-external-commands --no-aliases <<-\EOF &&
+	See '\''git help <command>'\'' to read about a specific subcommand
+
+	Main Porcelain Commands
+
+	Ancillary Commands / Manipulators
+
+	Ancillary Commands / Interrogators
+
+	Interacting with Others
+
+	Low-level Commands / Manipulators
+
+	Low-level Commands / Interrogators
+
+	Low-level Commands / Syncing Repositories
+
+	Low-level Commands / Internal Helpers
+	EOF
+	test_cmp expect actual
+'
+
 test_expect_success "'git help -g' section spacing" '
 	test_section_spacing_trailer git help -g <<-\EOF &&