help: add --config to list all available config

Sometimes it helps to list all available config vars so the user can
search for something they want. The config man page can also be used
but it's harder to search if you want to focus on the variable name,
for example.

This is not the best way to collect the available config since it's
not precise. Ideally we should have a centralized list of config in C
code (pretty much like 'struct option'), but that's a lot more work.
This will do for now.

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

1 files changed, 56 insertions, 0 deletions

diff --git a/help.c b/help.c
index dd35fcc133..f078dfebad 100644
--- a/help.c
+++ b/help.c
@@ -409,6 +409,62 @@ void list_common_guides_help(void)
 	putchar('\n');
 }
 
+struct slot_expansion {
+	const char *prefix;
+	const char *placeholder;
+	void (*fn)(struct string_list *list, const char *prefix);
+	int found;
+};
+
+void list_config_help(void)
+{
+	struct slot_expansion slot_expansions[] = {
+		{ "advice", "*", list_config_advices },
+		{ "color.branch", "<slot>", list_config_color_branch_slots },
+		{ "color.decorate", "<slot>", list_config_color_decorate_slots },
+		{ "color.diff", "<slot>", list_config_color_diff_slots },
+		{ "color.grep", "<slot>", list_config_color_grep_slots },
+		{ "color.interactive", "<slot>", list_config_color_interactive_slots },
+		{ "color.status", "<slot>", list_config_color_status_slots },
+		{ "fsck", "<msg-id>", list_config_fsck_msg_ids },
+		{ "receive.fsck", "<msg-id>", list_config_fsck_msg_ids },
+		{ NULL, NULL, NULL }
+	};
+	const char **p;
+	struct slot_expansion *e;
+	struct string_list keys = STRING_LIST_INIT_DUP;
+	int i;
+
+	for (p = config_name_list; *p; p++) {
+		const char *var = *p;
+		struct strbuf sb = STRBUF_INIT;
+
+		for (e = slot_expansions; e->prefix; e++) {
+
+			strbuf_reset(&sb);
+			strbuf_addf(&sb, "%s.%s", e->prefix, e->placeholder);
+			if (!strcasecmp(var, sb.buf)) {
+				e->fn(&keys, e->prefix);
+				e->found++;
+				break;
+			}
+		}
+		strbuf_release(&sb);
+		if (!e->prefix)
+			string_list_append(&keys, var);
+	}
+
+	for (e = slot_expansions; e->prefix; e++)
+		if (!e->found)
+			BUG("slot_expansion %s.%s is not used",
+			    e->prefix, e->placeholder);
+
+	string_list_sort(&keys);
+	for (i = 0; i < keys.nr; i++)
+		puts(keys.items[i].string);
+	string_list_clear(&keys, 0);
+}
+
 void list_all_cmds_help(void)
 {
 	print_cmd_by_category(main_categories);