Is this even possible? The API is accepting path relative to the build context.

Hi Petr,

Sorry for the misleading issue title.
Let me describe the problem which appeared in Docker after migrating from File to FileObject:
Before migration we made it possible to specify both relative and absolute path to Dockerfile, with known build context.
After migration this logic was just removed for some reason, see lines in changeset [1], like:
... if (!file.isAbsolute()) ...

Of course Build Image Wizard didn't work well without this logic. I.e. specifying in UI

Build Context = /home/user/docker/
Dockerfile    = /home/user/docker/Dockerfile

led to computing absolute path of Dockerfile as /home/user/docker//home/user/docker/Dockerfile
which is not correct.

I decided to store only absolute paths in BuildImageWizard, thus everyone who use this property
is sure that path is absolute. This eliminates code like:

                String file;
                if (dockerfile != null) {
                    file = buildContext + "/" + dockerfile;
                } else {
                    file = buildContext + "/" + DockerAction.DOCKER_FILE;
                }

As you correctly noted API is only accepting a relative path of Dockerfile to Build Context.
The relative path is now computed only once, before creating a build task. See changeset [2]

[1] http://hg.netbeans.org/cnd-main/rev/4c4f992549bc
[2] http://hg.netbeans.org/cnd-main/rev/b2ea7738c04b

Integrated into 'main-silver', will be available in build *201704230002* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)

Changeset: http://hg.netbeans.org/main-silver/rev/b2ea7738c04b
User: Ilia Gromov <ilia@netbeans.org>
Log: Fixed #270455 - For building image task: pass absolute dockerfile path instead of relative