Re: [PATCH v4 7/9] hook: replace run-command.h:find_hook

+int hook_exists(const char *hookname)
+{
+	const char *value = NULL;
+	struct strbuf hook_key = STRBUF_INIT;
+	strbuf_addf(&hook_key, "hook.%s.command", hookname);
+
+	return (!git_config_get_value(hook_key.buf, &value)) || !!find_hook(hookname);
+}

I was surprised that this didn't share code with hook_list. Upon further
thought, hook_list might be expensive if hooks are present, but if we
can cache results, I think it's worth it. A caller that calls this
function usually will run hooks if they are present, so it's not wasted
work to construct the hook list.