hex: handle support files with macro in umbrellas

[nirev]

This PR adds support for handling required files when a __DIR__ macro is used.
It also handles required files in umbrellas

The test case added extends the umbrella context with the following change:
apps/bank_web/mix.exs

defmodule BankWeb.Mixfile do
  use Mix.Project
  @something Code.eval_file("../../evaled.exs", __DIR__)

  def project do
    ..

docs for __DIR__: https://hexdocs.pm/elixir/Kernel.SpecialForms.html#__DIR__/0

[nirev]

scans mix.exs files in umbrellas for support files too

[nirev]

replaces the __DIR__ macro with the file dirname, so that in /apps/my_app/mix.exs

Code.eval_file("../../script.exs", __DIR__)

becomes

Code.eval_file("../../script.exs", "/apps/my_app")

[nirev]

I haven't got any comments here, so wondering if this contribution is something that the maintainers think it's worth adding.

I had an issue with a client's repo that was using something like this and I've changed it not eval the file when running on dependabot, but I think it would be cleaner if dependabot handled it.

[jurre]

I haven't got any comments here, so wondering if this contribution is something that the maintainers think it's worth adding.

I had an issue with a client's repo that was using something like this and I've changed it not eval the file when running on dependabot, but I think it would be cleaner if dependabot handled it.

Yep it definitely looks useful to me, thanks @nirev

In some ecosystems we've started just performing a (shallow) clone vs this custom file fetching logic, and I contemplated suggesting that, but I think it might end up being a larger change that's a bit more involved to roll out, so this seems like a good fix to me 👍

[nirev]

Thank you, @jurre!