Implement installation patching

[celer]

So I'd like to suggest a post installation patch functionality.

(there might be a better way to do this, I just don't know what it is)

Recently I struggled with a simple bug in a package that was 3 levels down as dependency.

The bug was in combined-stream which had a dependency chain like so:

request -> form-data -> combined-stream

So to resolve the bug meant I had to work up the tree, and each package had various challenges.

First I had to get the original issue fixed:
felixge/node-combined-stream#4

Then resulting in discovering that form-data had a hard coded version of node-combined-stream, so that had to be fixed.

Then I found out that request bundled its dependencies
request/request#431

This fix took me quite a while to get implemented as I needed to work with each package maintainer, to get the simple one line fix in place.

It would be awesome if post installation patches could be specified for a specific package based upon an included patch or pull request, so for example in my package.json:

patch: {
   'combined-stream@0.0.3': [ 'https://github.com/felixge/node-combined-stream/pull/4', 'patch.diff']
}

Which would apply the specified merge requests / patches post installation of a package when the matching version if the package is installed as dependency anywhere in the tree. Perhaps even allow the tree to be specified:

patch: { 
 'request/form-data/combined-stream@0.0.3':...
}

Initially I wrote some post install scripts to do this but I wasn't ever able to get it working exactly like I wanted and had issues with it implementing the changes I was after.

[luk-]

When I run into a dependency issue like the one you're describing I usually fork the repo, fix the bug, and point my package.json to it until the upstream is fixed and published. This is an interesting idea but I wonder if it would make things super confusing (with a lot of patching going on).

[edef1c]

I don't think this'll happen. Try @st-luke's approach.

[celer]

So originally I was hoping to use @st-luke approach, but then I discovered I was gonna have to fork a lot of repos to make it work. I should have tried that to see how it was living with that fix.

Thanks