var ErrFileOverDir = errors.New(
	"fsync: trying to overwrite a non-empty directory with a file")

type FileInfo interface {
	Name() string
	IsDir() bool
}

type Syncer struct {
	// Set this to true to delete files in the destination that don't exist
	// in the source.
	Delete bool
	// To allow certain files to remain in the destination, implement this function.
	// Return true to skip file, false to delete.
	// Note that src may be either os.FileInfo or fs.DirEntry depending on the file system.
	DeleteFilter func(f FileInfo) bool
	// By default, modification times are synced. This can be turned off by
	// setting this to true.
	NoTimes bool
	// NoChmod disables permission mode syncing.
	NoChmod bool
	// Implement this function to skip Chmod syncing for only certain files
	// or directories. Return true to skip Chmod.
	ChmodFilter func(dst, src os.FileInfo) bool

	SrcFs  afero.Fs
	DestFs afero.Fs
}