completion: allow to customize the completable command list

By default we show porcelain, external commands and a couple others
that are also popular. If you are not happy with this list, you can
now customize it a new config variable.

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

Documentation/config.txt

@@ -1343,6 +1343,14 @@ credential.<url>.*::
 credentialCache.ignoreSIGHUP::
 	Tell git-credential-cache--daemon to ignore SIGHUP, instead of quitting.
 
+completion.commands::
+	This is only used by git-completion.bash to add or remove
+	commands from the list of completed commands. Normally only
+	porcelain commands and a few select others are completed. You
+	can add more commands, separated by space, in this
+	variable. Prefixing the command with '-' will remove it from
+	the existing list.
+
 include::diff-config.txt[]
 
 difftool.<tool>.path::

Documentation/git.txt

@@ -170,7 +170,8 @@ foo.bar= ...`) sets `foo.bar` to the empty string which `git config
 	parse-options), main (all commands in libexec directory),
 	others (all other commands in `$PATH` that have git- prefix),
 	list-<category> (see categories in command-list.txt),
-	nohelpers (exclude helper commands) and alias.
+	nohelpers (exclude helper commands), alias and config
+	(retrieve command list from config variable completion.commands)
 
 GIT COMMANDS
 ------------

contrib/completion/git-completion.bash

@@ -3012,7 +3012,7 @@ __git_main ()
 			then
 				__gitcomp "$GIT_TESTING_PORCELAIN_COMMAND_LIST"
 			else
-				__gitcomp "$(git --list-cmds=list-mainporcelain,others,nohelpers,alias,list-complete)"
+				__gitcomp "$(git --list-cmds=list-mainporcelain,others,nohelpers,alias,list-complete,config)"
 			fi
 			;;
 		esac

git.c

@@ -77,6 +77,8 @@ static int list_cmds(const char *spec)
 			exclude_helpers_from_list(&list);
 		else if (match_token(spec, len, "alias"))
 			list_aliases(&list);
+		else if (match_token(spec, len, "config"))
+			list_cmds_by_config(&list);
 		else if (len > 5 && !strncmp(spec, "list-", 5)) {
 			struct strbuf sb = STRBUF_INIT;
 

help.c

@@ -366,6 +366,39 @@ void list_cmds_by_category(struct string_list *list,
 	}
 }
 
+void list_cmds_by_config(struct string_list *list)
+{
+	const char *cmd_list;
+
+	/*
+	 * There's no actual repository setup at this point (and even
+	 * if there is, we don't really care; only global config
+	 * matters). If we accidentally set up a repository, it's ok
+	 * too since the caller (git --list-cmds=) should exit shortly
+	 * anyway.
+	 */
+	if (git_config_get_string_const("completion.commands", &cmd_list))
+		return;
+
+	string_list_sort(list);
+	string_list_remove_duplicates(list, 0);
+
+	while (*cmd_list) {
+		struct strbuf sb = STRBUF_INIT;
+		const char *p = strchrnul(cmd_list, ' ');
+
+		strbuf_add(&sb, cmd_list, p - cmd_list);
+		if (*cmd_list == '-')
+			string_list_remove(list, cmd_list + 1, 0);
+		else
+			string_list_insert(list, sb.buf);
+		strbuf_release(&sb);
+		while (*p == ' ')
+			p++;
+		cmd_list = p;
+	}
+}
+
 void list_common_guides_help(void)
 {
 	struct category_description catdesc[] = {

help.h

@@ -26,6 +26,7 @@ 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 void list_cmds_by_config(struct string_list *list);
 extern const char *help_unknown_cmd(const char *cmd);
 extern void load_command_list(const char *prefix,
 			      struct cmdnames *main_cmds,