Build command fails when symlinks in docker folder are used

My Docker image includes some files, which are symlinks pointing outside of docker folder, e.g.

$ ls -l include/
total 0
lrwxrwxrwx 1 dmitry dmitry 29 Mar 30 17:25 python3.5m -> /usr/local/include/python3.5m

Native docker client handles this correctly. Java File.getCanonicalFile() follows symlinks, so TAR archive sent to Docker daemon contains usr/local/include/python3.5m/** instead of expected include/python3.5m/**, and as a result I get confusing errors about non-existent files.

I guess replacing FilePathUtil.relativize(File, File) with the following code would work, but please check if this behavior does not break other usages.

    public static String relativize(File baseDir, File file) {
        try {
            return baseDir.toPath()
                          .toRealPath(LinkOption.NOFOLLOW_LINKS)
                          .relativize(file.toPath().toRealPath(LinkOption.NOFOLLOW_LINKS))
                          .toString();
        } catch (IOException e) {
            throw new DockerClientException(e.getMessage(), e);
        }
    }

[hugares]

Ok, the pull request https://github.com/docker-java/docker-java/pull/1211 fixed the unit tests as mentioned before and I also added the many tests to increase coverage to cover the tar created and passed to the docker daemon. I will work on fixing the issue now.

[hugares]

The pull request is related to this bug because I fixed the units tests that now fails because symlink are not preserved. The only thing is the unit tests are testing CompressArchiveUtil.tar method which is not the method used when sending the docker build folder to docker daemon.

I will either add tests for CompressArchiveUtil.archiveTARFiles or rework both methods to remove the code duplication and then I will fix code to preserve symlinks.