There are two important branches in this repository.
The release branch
This is the code were the Docker image published on Docker Hub is built from.
It must only contain stable code and the most recent commit should be the commit increasing the version number in the VERSION file.
The develop branch
It is where all the PRs land.
When it is decided that enough features have landed, a release is cut.
Reason
We once had the master branch.
The master branch was the basis for the Docker builds.
So when we merged features there, they were added to the Docker image immediately.
To get around this we merged all relevant PRs manually and at once, then we cut a release and pushed all the features together to the master branch.
That was not a nice workflow, also because that way PRs were kept open for a long time.
So we introduced the release and develop branches as described above.