I completely agree. If you're going to add generated files to a source code repository, they need to be clearly marked in one way or another.

If the author truly want a "go generate" they good sell it much better. I understand the yacc idea, it can be a pretty good solution for something like configuration files. OpenBSD use yacc to do the grammar for many of they tools and that has worked out create.

The big sell though would be WSDLs. I understand the aversion towards SOAP and WSDL, but it's here and having Go support would be nice. Generating Go code from a WSDL wouldn't be to hard a sell I think, and it fits nicely into this idea.