feat: add a hook to modify dependency manifests

[zkochan]

Ref pnpm/pnpm#861

[zkochan]

Hey, @vjpr and @andreineculau.

This PR adds a hook to pnpm's installation engine for rewriting dependencies' manifests.

pnpm will probably require a pnpm.js file from the root of the package, if available, and hooks or other configs will be exported by that file. That will be another PR in the pnpm repo

[andreineculau]

this looks fantastic! need to try it out but a glimpse through the diff passed my mental compiler

[zkochan]

I think this hook will be super powerfull with the alias feature added: pnpm/pnpm#837

I'm not sure though how to implement that. Maybe through another hook

[vjpr]

Looks really cool!

pnpm will probably require a pnpm.js file

I vote for pnpm.config.js.

[zkochan]

I called it pnpmfile.js. Here's the change: pnpm/pnpm@0330ff0

I published the change with pnpm version 1.12.0 and posted an article about it: Why package managers need hook systems

[andreineculau]

I would have also +1 ed the pnpm.config.js (or pnpmrc.js or pnpm.js or the dotted variants) but it's not the end of the world. It's just both not clear (what it does, how do you write it : pnpm-file like in the comment above or pnpmfile), and overly verbose (a file called *file*).

[zkochan]

It can be changed. The reason I did not call it with the rc or config suffix is that we use npm's config system which uses .npmrc files.

The file suffix is used by gulpfile.js, Gruntfile.js, Dockerfile. So it seemed to me like a convention.

If any of you would really prefer a different name, please create an issue and we'll make a vote or something like that.