# Builds a skill source directory into a derivation, `SKILL.md` at the `$out` root.
{
  pkgs,
  src,
  name ? builtins.baseNameOf (toString src),
}:
pkgs.stdenvNoCC.mkDerivation {
  inherit name src;

  # A skill is just files to copy, with nothing to unpack, configure, or build.
  dontUnpack = true;
  dontConfigure = true;
  dontBuild = true;

  installPhase = ''
    runHook preInstall
    mkdir -p "$out"
    cp -R "$src"/. "$out/"
    test -f "$out/SKILL.md" \
      || { echo "mkSkill: skill '${name}' has no SKILL.md at its root" >&2; exit 1; }
    runHook postInstall
  '';

  # The name as an eval-time attribute, readable without building `$out`
  # (no import-from-derivation).
  passthru.skillName = name;
}