Support ~ in path for dependencies

[Wasabi375]

Problem

I would like to specify a dependency relative to my home directory. At the moment I would need to specify the home directory as a full path which is platform dependent, e.g Linux

my_dep = { path = "/home/name/rust/my_dep" }

Proposed Solution

Most shells expand ~ into the current users home directory. It would be nice if cargo could do the same.

my_dep = { path = "~/rust/my_dep" }

That would than be expanded into the user home directory.

Notes

Currently ~/something is resolved to project-dir/~/something which is obviously not what is intended by the user.

Also looking through existing issues, this might be the same as #12873

[epage]

Could you expand on your use case for why you are using absolute paths in dependencies?

For myself, my projects tend to be in repos and shared with others, so I can't count on an absolute path being there, only relative paths to other items within my repo. If I need to reference something outside my repo, it then needs to be a git dependency.

[weihanglo]

FWIW, previously we had #9855 and rust-lang/rfcs#3074.

[Wasabi375]

My use case is the following:

I had a problem with a library: In this case rust-derive-builder.
Created a small test project to reproduce the issue.
After some discussion I started working on a fix.
Now I want to use my local implementation of rust-derive-builder in my test project to ensure that I have a working solution.

Maybe a better solution would be to just copy my minimal test case into a proper test within the library.
That said I was still surprised about the fact that ~ is not handled the way I would expect it to. I always assumed that ~ was a special character in paths and only learned that ~ is a shell feature, after googling for it when creating this issue.

[epage]

Thanks for explaining, that helps a lot in understanding how someone would run into this in day-to-day operations.

On the broader side of this topic, I've wondered if we could have an improved workflow around patching, like a new subcommand that would make it easy to patch a dependency to an in-dev version, then clone that dependency so you can make a change, and then back this out of your project. We have issues like #1545 and #1861 which tie into that.