feat: add EXTRA_NIX_CONFIG variable

[Defelo]

No description provided.

[MattSturgeon]

Nice feature!

[MattSturgeon]

Is it intended that the target branch is push-mllzlywwyzum, rather than main?

[Defelo]

Is it intended that the target branch is push-mllzlywwyzum, rather than main?

Yes, unfortunately GitHub doesn't really supported stacked PRs, so if you have a PR "A" and use that as the base of another PR "B", GH includes the changes of "A" in the diff view of "B", if both of them use main as the base branch. Also, if you merge "A" now, by doing a fast forward, GitHub doesn't update the diff of "B" (and any descendants) and still includes the commits and changes of "A". But if you set the base branch of "B" to the branch of "A", only those commits that are in "B" but not in "A" are shown in the diff view of "B", and if "A" is merged and the branch of "A" is deleted, GH automatically updates "B" to instead target the main branch (see #62 for example).

[cameronraysmith]

Works for me. Many thanks for this Defelo.
Resolves #49.

[cameronraysmith]

From the gh cli you can set this via

gh variable set -R [fork-username]/nixpkgs-review-gha EXTRA_NIX_CONFIG <<'EOF'
extra-substituters = https://nix-community.cachix.org
extra-trusted-public-keys = nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs=
EOF

and then you should find something like the following in the workflow run logs

Run cachix/install-nix-action@v31
  with:
    extra_nix_config: build-dir = /nix/build
  sandbox = true
  system = x86_64-linux
  extra-substituters = https://nix-community.cachix.org/
  extra-trusted-public-keys = nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs=
  
    enable_kvm: true
    set_as_trusted_user: true
  env:
    PR_NUMBER: NNNNNN
    TMPDIR: /mnt/tmp.jqTjgZ6hYE