pkgs/top-level/metrics.nix: just run nix-env -qa once

      shift

      echo "running $@"

      local output="$name.out"

      local nix_stats="$name-nix-stats.json"

      local time_stats="$name-time-stats.json"

      case "$name" in

        # Redirect stdout to /dev/null to avoid hitting "Output Limit Exceeded" on Hydra.

        nix-env.qaDrv)

          NIX_SHOW_STATS=1 NIX_SHOW_STATS_PATH="$nix_stats" time -o "$time_stats" "$@" >/dev/null ;;

        *)

          NIX_SHOW_STATS=1 NIX_SHOW_STATS_PATH="$nix_stats" time -o "$time_stats" "$@" ;;

      esac

      NIX_SHOW_STATS=1 NIX_SHOW_STATS_PATH="$nix_stats" time -o "$time_stats" "$@" > "$output"

      # Show the Nix statistics and the `time` statistics.

      echo "Nix statistics for $@"

    run nix-env.qaDrv nix-env --option eval-system "$evalSystem" -f "$nixpkgs" -qa --drv-path --meta --json

    # It's slightly unclear which of the set to track: qaCount, qaCountDrv, qaCountBroken.

    num="$(nix-env --option eval-system "$evalSystem" -f "$nixpkgs" -qa | wc -l)"

    num="$(wc -l < nix-env.qa.out)"

    echo "nix-env.qaCount $num" >> $out/nix-support/hydra-metrics

    qaCountDrv="$(nix-env --option eval-system "$evalSystem" -f "$nixpkgs" -qa --drv-path | wc -l)"

    num="$((num - $qaCountDrv))"

    echo "nix-env.qaCountBroken $num" >> $out/nix-support/hydra-metrics

    qaCountDrv="$(jq -r 'reduce .[].drvPath as $d (0; .+1)' < nix-env.qaDrv.out)"

    numBroken="$((num - $qaCountDrv))"

    echo "nix-env.qaCountBroken $numBroken" >> $out/nix-support/hydra-metrics

    lines="$(find "$nixpkgs" -name "*.nix" -type f | xargs cat | wc -l)"

    echo "loc $lines" >> $out/nix-support/hydra-metrics