type Entry struct {
	Kind    EntryKind
	Symlink string
}

type EntryKind uint8

const (
	DirEntry  EntryKind = 1
	FileEntry EntryKind = 2
)

type FS interface {
	// The returned map is immutable and is cached across invocations. Do not
	// mutate it.
	ReadDirectory(path string) map[string]Entry
	ReadFile(path string) (string, bool)

	// This is part of the interface because the mock interface used for tests
	// should not depend on file system behavior (i.e. different slashes for
	// Windows) while the real interface should.
	Abs(path string) (string, bool)
	Dir(path string) string
	Base(path string) string
	Ext(path string) string
	Join(parts ...string) string
	Cwd() string
	Rel(base string, target string) (string, bool)
}