Enhance direct Dockerfile support

The following features should be added for a better experience when using Dockerfiles directly:

• It should be possible to support multiple Dockerfiles (as Docker 1.6 does). The idea is to use dockerFile instead of dockerFileDir and the base directory is then set to the directory of this Dockerfile (if dockerFileDir is used, then the name of the dockerfile is supposed to be Dockerfile)
• Allow variable substitution within Dockerfiles (as for other Maven resources).
• Allows special variables for:
  • ADD_ASSEMBLY will add the proper ADD statements for the assmbly
• Allow the configuration of the assembly directory used during the build. See also #203
• Optional: Allow optimizations like compressing all subsequent RUN statements into a single RUN statement or so.

[adam42a]

If you could add some logging output as follows, it’d probably save a few people some time.

What threw me is that d-m-p creates a temporary directory but in dockerFileMode

target/<dockerOutputDirectory>/<imageName>/build

and it puts the Dockerfile in there, but it doesn’t include the other files which are in <dockerFileDir>

The only way to be sure that they were included was to either run the image and see if it died, or attach to the image and look around, or open up the outputDirectory.tar with 7zip and check.

It would be cool if there was some logging at info level rather than just the following (I use verbose=true) :

[INFO] --- docker-maven-plugin:0.22.1:build (build-docker-image) @ tardis --- [INFO] Building tar: C:\dev\workspace\tardis\target\docker-build\xyz987\tmp\docker-build.tar [INFO] DOCKER> [xyz987/tardis:latest]: Created docker-build.tar in 170 milliseconds

[rhuss]

Reiterating on the Dockerfile support in general, I have more and more the feeling that we should separate the two ways of building images more prominently (and not only by a low-level dockerFileDir which can be easily overlooked). Also because of potentially other ways to build images (see e.g. #414)

We could add extra configuration field <dockerfileBuild> on the same level as <build> for make the distinction clear. This could work also with a <type> field in the <build> section, but that would not easily be backwards compatible.

Thoughts on this ?