Sync deployment jobs

[lurtz]

Deployment jobs modify the gh-pages branch and concurrent modification needs to be prevented. Otherwise we get random build failures.

Note: I have not tested this myself and I actually do not want to because testing it is quite time consuming. This solutions is what came to my mind after analyzing the logs of eclipse-score/docs-as-code#404

Closes eclipse-score/docs-as-code#404

[AlexanderLanin]

Is this better/worse/different than job.concurrency?

[lurtz]

Is this better/worse/different than job.concurrency?

@AlexanderLanin I was not aware of that. Its documentation says the following:

When a concurrent job or workflow is queued, if another job or workflow using the same concurrency group in the repository is in progress, the queued job or workflow will be pending. Any existing pending job or workflow in the same concurrency group, if it exists, will be canceled and the new queued job or workflow will take its place.

This seems not to be the behavior we want for updating the gh-pages branch. This would mean some pull requests will have eventually no documentation deployed to that branch.

I think a better application of this option is e.g. checking branches while new commits are pushed.