// check both fileInfo's have same number of versions, if not skip
	// the `other` entry.
	if len(eVers.versions) != len(oVers.versions) {
		eTime := eVers.latestModtime()
		oTime := oVers.latestModtime()
		if !eTime.Equal(oTime) {
			if eTime.After(oTime) {
				return e, false
			}
			return other, false
		}
		// Tiebreak on version count.
		if len(eVers.versions) > len(oVers.versions) {
			return e, false
		}

	AppendFile(ctx context.Context, volume string, path string, buf []byte) (err error)
	CreateFile(ctx context.Context, origvolume, olume, path string, size int64, reader io.Reader) error
	ReadFileStream(ctx context.Context, volume, path string, offset, length int64) (io.ReadCloser, error)
	RenameFile(ctx context.Context, srcVolume, srcPath, dstVolume, dstPath string) error