core/pkgs/build-support/fetchgithub/default.nix

{ lib, fetchgit, fetchzip }:

lib.makeOverridable ({ owner, repo, rev, name ? "source"
  , fetchSubmodules ? false, leaveDotGit ? null, deepClone ? false
  , private ? false, forceFetchGit ? false, sparseCheckout ? [ ]
  , githubBase ? "github.com", varPrefix ? null, meta ? { }
  , ... # For hash agility
  }@args:

  let

    position = (if args.meta.description or null != null then
      builtins.unsafeGetAttrPos "description" args.meta
    else
      builtins.unsafeGetAttrPos "rev" args);
    baseUrl = "https://${githubBase}/${owner}/${repo}";
    newMeta = meta // {
      homepage = meta.homepage or baseUrl;
    } // lib.optionalAttrs (position != null) {
      # to indicate where derivation originates, similar to make-derivation.nix's mkDerivation
      position = "${position.file}:${toString position.line}";
    };
    passthruAttrs = removeAttrs args [
      "owner"
      "repo"
      "rev"
      "fetchSubmodules"
      "forceFetchGit"
      "private"
      "githubBase"
      "varPrefix"
    ];
    varBase = "NIX${
        lib.optionalString (varPrefix != null) "_${varPrefix}"
      }_GITHUB_PRIVATE_";
    useFetchGit = fetchSubmodules || (leaveDotGit == true) || deepClone
      || forceFetchGit || (sparseCheckout != [ ]);
    # We prefer fetchzip in cases we don't need submodules as the hash
    # is more stable in that case.
    fetcher = if useFetchGit then
      fetchgit
      # fetchzip may not be overridable when using external tools, for example nix-prefetch
    else if fetchzip ? override then
      fetchzip.override { withUnzip = false; }
    else
      fetchzip;
    privateAttrs = lib.optionalAttrs private {
      netrcPhase = ''
        if [ -z "''$${varBase}USERNAME" -o -z "''$${varBase}PASSWORD" ]; then
          echo "Error: Private fetchFromGitHub requires the nix building process (nix-daemon in multi user mode) to have the ${varBase}USERNAME and ${varBase}PASSWORD env vars set." >&2
          exit 1
        fi
        cat > netrc <<EOF
        machine ${githubBase}
                login ''$${varBase}USERNAME
                password ''$${varBase}PASSWORD
        EOF
      '';
      netrcImpureEnvVars = [ "${varBase}USERNAME" "${varBase}PASSWORD" ];
    };

    gitRepoUrl = "${baseUrl}.git";

    fetcherArgs = (if useFetchGit then
      {
        inherit rev deepClone fetchSubmodules sparseCheckout;
        url = gitRepoUrl;
      } // lib.optionalAttrs (leaveDotGit != null) { inherit leaveDotGit; }
    else {
      url = "${baseUrl}/archive/${rev}.tar.gz";

      passthru = { inherit gitRepoUrl; };
    }) // privateAttrs // passthruAttrs // {
      inherit name;
    };

  in fetcher fetcherArgs // {
    meta = newMeta;
    inherit rev owner repo;
  })