fix: cannot find package.json on ESM

[jopemachine]

Fixes #2122.

In the case of ava, mainFilename changes like below way.

// existing code's value:
mainFilename: /usr/local/lib/

// this PR's value:
mainFilename: /usr/local/lib/node_modules/ava/

This enable yargs to find ava's package.json properly.

[bcoe]

@jopemachine I don't fully understand this fix, is the issue that there are multiple instances of node_modules in the path?

[jopemachine]

I don't fully understand this fix, is the issue that there are multiple instances of node_modules in the path?

Yes, as I mentioned in this comment, node_modules appears more than once in the path (__dirname).

So, existing code can't find proper mainFilename, package.json, that's why globally installed this module's version command prints unknown.

[jamescdavis]

@bcoe I tested this fix and I can confirm that it fixes the issue. Seems like a good solution. Hopefully this can be merged and released soon. 🙂

[bcoe]

@jopemachine nit, it would be nice to have a test for this, but going ahead and merging with the hopes of unblocking issues with ava.

apologies for the slow review.