git: support --list-cmds=list-<category>

This allows us to select any group of commands by a category defined
in command-list.txt. This is an internal/hidden option so we don't
have to be picky about the category name or worried about exposing too
much.

This will be used later by git-completion.bash to retrieve certain
command groups.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git.txt

@@ -168,7 +168,8 @@ foo.bar= ...`) sets `foo.bar` to the empty string which `git config
 	option and may change or be removed in the future. Supported
 	groups are: builtins, parseopt (builtin commands that use
 	parse-options), main (all commands in libexec directory),
-	others (all other commands in `$PATH` that have git- prefix).
+	others (all other commands in `$PATH` that have git- prefix),
+	list-<category> (see categories in command-list.txt)
 
 GIT COMMANDS
 ------------

generate-cmdlist.sh

@@ -45,6 +45,21 @@ define_categories () {
 	test "$bit" -gt 32 && die "Urgh.. too many categories?"
 }
 
+define_category_names () {
+	echo
+	echo "/* Category names */"
+	echo "static const char *category_names[] = {"
+	bit=0
+	category_list "$1" |
+	while read cat
+	do
+		echo "	\"$cat\", /* (1UL << $bit) */"
+		bit=$(($bit+1))
+	done
+	echo "	NULL"
+	echo "};"
+}
+
 print_command_list () {
 	echo "static struct cmdname_help command_list[] = {"
 
@@ -70,4 +85,6 @@ struct cmdname_help {
 "
 define_categories "$1"
 echo
+define_category_names "$1"
+echo
 print_command_list "$1"

git.c

@@ -60,6 +60,13 @@ static int list_cmds(const char *spec)
 			list_all_main_cmds(&list);
 		else if (match_token(spec, len, "others"))
 			list_all_other_cmds(&list);
+		else if (len > 5 && !strncmp(spec, "list-", 5)) {
+			struct strbuf sb = STRBUF_INIT;
+
+			strbuf_add(&sb, spec + 5, len - 5);
+			list_cmds_by_category(&list, sb.buf);
+			strbuf_release(&sb);
+		}
 		else
 			die(_("unsupported command listing type '%s'"), spec);
 		spec += len;

help.c

@@ -329,6 +329,29 @@ void list_all_other_cmds(struct string_list *list)
 	clean_cmdnames(&other_cmds);
 }
 
+void list_cmds_by_category(struct string_list *list,
+			   const char *cat)
+{
+	int i, n = ARRAY_SIZE(command_list);
+	uint32_t cat_id = 0;
+
+	for (i = 0; category_names[i]; i++) {
+		if (!strcmp(cat, category_names[i])) {
+			cat_id = 1UL << i;
+			break;
+		}
+	}
+	if (!cat_id)
+		die(_("unsupported command listing type '%s'"), cat);
+
+	for (i = 0; i < n; i++) {
+		struct cmdname_help *cmd = command_list + i;
+
+		if (cmd->category & cat_id)
+			string_list_append(list, drop_prefix(cmd->name));
+	}
+}
+
 int is_in_cmdlist(struct cmdnames *c, const char *s)
 {
 	int i;

help.h

@@ -21,6 +21,8 @@ static inline void mput_char(char c, unsigned int num)
 extern void list_common_cmds_help(void);
 extern void list_all_main_cmds(struct string_list *list);
 extern void list_all_other_cmds(struct string_list *list);
+extern void list_cmds_by_category(struct string_list *list,
+				  const char *category);
 extern const char *help_unknown_cmd(const char *cmd);
 extern void load_command_list(const char *prefix,
 			      struct cmdnames *main_cmds,