coverage map path in extended configs should be relative to the extended config, not the original config

[isaacs]

I have a monorepo where each workspace has "tap": { "extends": "../../.taprc" } in their package.json.

Then, in the root, i have a ./coverage-map.js and a .taprc. I'd like that .taprc to have coverage-map: ./coverage-map.js, but that would be wrong, because it'd resolve the file against the original config, not the extended config.

This makes it annoying to have a package or other external config that contains a coverage map, because it'd have to know where it's being imported from.

Solution: coverage-map config should be resolved against the config being applied. Same with a reporter that's a relative path.

The include and exclude should still be relative to the project, because that's where they'd live, not in an extended config.