Proper Docker tags for images

[asoltesz]

Currently, it seems that Docker HUB tagging for OpenHAB is not according to best practices and semantic versioning.

For example: the tag 2.4.0 was updated 5 days ago, although there was a much older original version of this tag (and probably several versions in between).

A tag that gets updated like this should be called "2.4-latest" or "2.4.x", clearly marking that this is continuously updated.

If there is a patch release of OpenHAB, which is then released as a Docker image, its tag should follow the patch version of OpenHAB (e.g.: 2.4.1). Docker tags like this are supposed to be immutable and only image-building error fixes should change it (if they happen at all).

With the current system, deployments behave unpredictably because several, slightly different versions can easily be present on my developer machine and on deployed environments (without being obvious why this happens)

[cniweb]

The Docker HUB tagging and the versions of OpenHAB are actually identical.
The fact that the tags were newly built is actually only due to error corrections or changes for the image creation.

[wborn]

To improve this with the current build setup we could detect which files are changed and only rebuild the impacted images. We use something similar in openhab-addons. Normally if the build is triggered by Jenkins, Travis should only rebuild the snapshot images instead of all images.

[cniweb]

Perhaps we should switch to building the Docker images on Maven with fabric8 plugin:
https://dmp.fabric8.io