(Provide option to) ignore empty files

[afq984]

Questions:

• Do we want this feature?
• Do we want an option for it?
• Do we want it enabled by default?

[flwyd]

This seems like a useful feature. I don't think an empty text file is a copyrightable work, so having nothing but a license in a file seems unnecessary.

This can probably be done automatically. Perhaps it should log a warning if it encounters a file which would get a license header but is empty; empty source files without even comments are unusual, so this might indicate an error downloading a project.

If there's a use case for adding license text to an empty file, I think that behavior should be opt-in with a flag.