Allow customizing fetchurl hashedMirrors (#409010)

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- Added `rewriteURL` attribute to the nixpkgs `config`, to allow for rewriting the URLs downloaded by `fetchurl`.

- Added `hashedMirrors` attribute to the nixpkgs `config`, to allow for customization of the hashed mirrors used by `fetchurl`.

- Added `gitConfig` and `gitConfigFile` option to the nixpkgs `config`, to allow for setting a default `gitConfigFile` for all `fetchgit` invocations.

  curl, # Note that `curl' may be `null', in case of the native stdenvNoCC.

  cacert ? null,

  rewriteURL,

  hashedMirrors,

}:

let

  mirrors = import ./mirrors.nix;

  mirrors = import ./mirrors.nix // {

    inherit hashedMirrors;

  };

  # Write the list of mirrors to a file that we can reuse between

  # fetchurl instantiations, instead of passing the mirrors to

{

  # Content-addressable Nix mirrors

  hashedMirrors = [

    "https://tarballs.nixos.org"

  ];

  hashedMirrors = throw "Use config.hashedMirrors instead of (import ./pkgs/build-support/fetchurl/mirrors.nix).hashedMirrors";

  # Mirrors for mirror://site/filename URIs, where "site" is

  # "sourceforge", "gnu", etc.

        ${jq}/bin/jq -r '.headers.Hello' $out | ${moreutils}/bin/sponge $out

      '';

    };

  # Tests that hashedMirrors works

  hashedMirrors = testers.invalidateFetcherByDrvHash fetchurl {

    # Make sure that we can only download from hashed mirrors

    url = "http://broken";

    # A file with this hash is definitely on tarballs.nixos.org

    sha256 = "1j1y3cq6ys30m734axc0brdm2q9n2as4h32jws15r7w5fwr991km";

    # No chance

    curlOptsList = [

      "--retry"

      "0"

    ];

  };

  # Tests that downloadToTemp works with hashedMirrors

  no-skipPostFetch = testers.invalidateFetcherByDrvHash fetchurl {

    # Make sure that we can only download from hashed mirrors

    # $downloadedFile, but here we know that because the URL is broken, it will

    # have to fallback to fetching the previously-built derivation from

    # tarballs.nixos.org, which provides pre-built derivation outputs.

  };

}

          inherit lib;

          stdenvNoCC = prevStage.ccWrapperStdenv or thisStdenv;

          curl = bootstrapTools;

          inherit (config) rewriteURL;

          inherit (config) hashedMirrors rewriteURL;

        };

        inherit cc;