add support for linked projects

[zimbatm]

This allows having links between different packages within a monorepo.

TODO: add tests

[asmundo]

hi @zimbatm any plan for adding tests?

hi @andir any plan to accept this change?

If a test is what is needed to get this merged. I MAY BE able to get help from people with npm knowledge and create a test..

[andir]

I think one of my main issues is that I don't know what this does. Is it for local references within the same repository? If so, lets add a test and document it properly (within the test) so that the next person doesn't have to reverse engineer the test to understand it. This is already far from ideal in terms of mental complexity.

[asmundo]

I created the smallest example I could come up with IIUC. I failed to integrate in to the testing. My nix is only so good. If you have some hints on how to create the nix part it would be appropriated! Happy to do it but it may take some times. If you just feel like doing that part yourself I am fine with that. A rewrite of testing framework to support this is outside of my Nix knowledge.

local-dependency.tar.gz

[asmundo]

Could be there is a test I can copy and modify with limited knowledge, is there?