document updated 15 years ago, on Oct 15, 2008
TODO: Produce a side-by-side comparison of the output of 'help' for all variants of GRUB. (see grub4dos's for example) Then post this to Wikipedia.
look in stage2/builtins.c, and search for "struct builtin" in each.
For GRUB 2, download the source, and mass-grep for grub_register_command().