Error during image build when Dockerfile in subdirectory of build context

Hello!

I try to build docker image with your library and think I found a bug.
I have such project structure:

/path/to/project/docker/Dockerfile
/path/to/project/target/app.jar

In my Dockerfile:

(...)
COPY target/app.jar /opt/app/app.jar
(...)

I try to build image with code:

final String baseDirectory = "/path/to/project";
final String dockerfile = baseDirectory + "/docker/Dockerfile";
dockerClient.buildImageCmd()
                .withBaseDirectory(new File(baseDirectory))
                .withDockerfile(new File(dockerfile))
                .exec()
                .awaitImageId();

I get error: Could not build image: lstat target/app.jar: no such file or directory

I think there is bug in class Dockerfile.
In method processAddStatement() is line

src = new File(dockerFolder, resource);

and dockerFolder is parent directory of Dockerfile. IMO it is incorrect, it should be

src = new File(baseDirectory, resource);

where baseDirectory is directory passed to method withBaseDirectory() of BuildImageCmd.

From command line build works with command

docker build -f docker/Dockerfile .