Resolve "Installation"

Closes #18 (closed)

inc/lektor/cmd.h

@@ -17,8 +17,12 @@ typedef void (*lkt_cmd_callback)(struct lkt_cmd_args *);
 struct lkt_cmd_opt {
     const char *name;
     lkt_cmd_callback call;
+    const char *help;
+    struct lkt_cmd_opt *sub;
 };
 
 /* Parse the command line with the list of options. No parameter may be NULL.
    Does not return. */
 noreturn void lkt_cmd_parse(struct lkt_cmd_opt *opts, int argc, const char **argv, void (*help)(void));
+
+void lkt_cmd_help(struct lkt_cmd_opt *opts, const char *name);