// Package tool defines stateful operation types for cue commands.
//
// This package is only visible in cue files with a _tool.cue or _tool_test.cue
// ending.
//
// CUE configuration files are not influenced by and do not influence anything
// outside the configuration itself: they are hermetic. Tools solve
// two problems: allow outside values such as environment variables,
// file or web contents, random generators etc. to influence configuration,
// and allow configuration to be actionable from within the tooling itself.
// Separating these concerns makes it clear to user when outside influences are
// in play and the tool definition can be strict about what is allowed.
//
// Tools are defined in files ending with _tool.cue. These files have a
// top-level map, "command", which defines all the tools made available through
// the cue command.
//
// The following definitions are for defining commands in tool files: