Documentation suggests that you can just name your group

[martinthomson]

Documentation:

You can put whatever value you want into the "Group" value, though. Unrecognized values will just use the default boilerplate files. If you want to add specialized boilerplate files for your group, check out the File-Based Includes section, later in this document, and write your own files.

Actuality:

FATAL ERROR: Unknown Group 'mygroup'. See docs for recognized Group values.

The documentation should reflect whatever reality exists.

However, I would also suggest that the documentation has the preferred state, not the code. The case where I observed this was perfectly able to use the "Org" metadata (set to "W3C") to obtain boilerplate. It should not be the case that you have to setup custom boilerplate for every use of the tool.

[tabatkins]

There's a trade-off here, between allowing unrecognized groups to still get the generic Org boilerplate, and catching unintentional typos. I know there were several specs misspelling their Groups, so I opted toward catching typos.

But you're right, I should continue to allow unrecognized groups somehow. (And update the docs, sorry about that.)