Add git commit SHA to Docker images

[shaneog]

Add the full git commit SHA to the generated Docker images using the
org.opencontainers.image.revision metadata label.

Fixes #865
Closes #892

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[shaneog]

@MarkEWaite Seems that tests are failing now due to a docker rate limit:

docker: Error response from daemon: toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit.```

[olivergondza]

I like this. Please fix the indent.

[MarkEWaite]

I'm willing to approve, but I'm unclear why the COMMIT_SHA is included in the Makefile when the JENKINS_SHA is not. I think that may need review from @timja or @dduportal

[timja]

The tests have a fixed Jenkins sha while the repo commit will change all the time.

[shaneog]

@MarkEWaite JENKINS_SHA is defined with a default value that can be overridden which is based on an external repository. You can see the overrides defined in several Dockerfile files.

COMMIT_SHA is based on this repository and so a static default cannot (and should not) be defined, therefore we must dynamically define it somewhere. The Makefile is the proper place to define this since it is the basis of all (most?) build commands used.

Note that I redefine it in .ci/publish.sh since it's possible that this script is called manually (as per the HACKING.adoc file).

[timja]

Love this, thanks for the tests too