private CopySession newCopySession(final String source) {
        final GetFileRequest.Builder reqBuilder = GetFileRequest.newBuilder() //
            .setFilename(source) //
            .setReaderId(this.readId);
        return new CopySession(this.rpcService, this.timerManager, this.snapshotThrottle, this.raftOptions, reqBuilder,
            this.endpoint);
    }
Copy `source` from remote to local dest.

@param source   source from remote
@param destPath local path
@param opts     options of copy
@return true if copy success
jraft-core/src/main/java/com/alipay/sofa/jraft/storage/snapshot/remote/RemoteFileCopier.java