Ava: Ignore underscore-prefixed directories

[sindresorhus]

AVA v2 removed the default ignore for directories named fixtures, which was a good change, but the result is that I now need to have AVA config in a lot of projects to ignore it manually. Would be nice if AVA had the underscore convention for directories too. Then I could just name the directory _fixtures. AVA would ignore all files inside a underscore-prefixed directory.

This would create a nice symmetry with the existing behavior for files:

Files with an underscore prefix are ignored. - https://github.com/avajs/ava/blob/master/docs/06-configuration.md

[novemberborn]

This would create a nice symmetry with the existing behavior for files:

Files with an underscore prefix are ignored. - https://github.com/avajs/ava/blob/master/docs/06-configuration.md

They are treated as helper files though. But I don't think we should do that for prefixed directories.

[shellscape]

I support allowing underscore-prefixed directories to be ignored. I don't agree that not ignoring fixtures by default was a good change (it actually wreaked a fair amount of havoc across our org and we still haven't fully updated to v2) but prefixing directories is a much easier way to go than updating config in many places.

[novemberborn]

With https://github.com/avajs/ava/pull/2323 AVA itself no longer has a concept of helpers, just files that are never test files. Once that lands, I'll try and add the checks described in this issue.

[novemberborn]

(Though the ESLint plugin helper does treat underscore-prefixed files as helpers.)