nixos/virtualisation/podman: add completion for dockerCompat (#446817)

  json = pkgs.formats.json { };

  inherit (lib) mkOption types;

  inherit (pkgs) stdenv;

  # Provides a fake "docker" binary mapping to podman

  dockerCompat =

    pkgs.runCommand "${cfg.package.pname}-docker-compat-${cfg.package.version}"

      {

        nativeBuildInputs = [ pkgs.installShellFiles ];

        outputs = [

          "out"

          "man"

          basename=$(basename $f | sed s/podman/docker/g)

          ln -s $f $man/share/man/man1/$basename

        done

      ''

    + lib.optionalString (!stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''

      export HOME=$(mktemp -d) # work around `docker <cmd>`

      installShellCompletion --cmd docker \

        --bash <($out/bin/docker completion bash) \

        --zsh <($out/bin/docker completion zsh) \

        --fish <($out/bin/docker completion fish)

    '';

in