Receive all tags, filtered by branch origin

First of all, I’m not sure about the correct category, so sorry if it’s in the wrong one…

We have three branches, the Master, Testing and Development. Most of the systems will be using the Master branch to update their system, but not all. Some systems will be using the Testing branch to update the system. That’s the easy part.

We are using Tags to determine certain “Update points”, to where the system can go to (update and/or downgrade). The update part is working, but I’m stuck with the tags.

We create tags for every Master release, and every Testing release. Once the testing has been done, the testing branch will be merged with the master branch.

But when I do a API call to the in-house GitLab server, I receive all the tags, but I can’t find out a way to filter on a specific branch (Get all the tags from the testing branch).

I tried to create a own API call, but I can’t figure out how the filtering can be done. I’m working on it for a week now, but I have the feeling this isn’t getting anywhere.

Am I right? Is this not possible with Git / Gitlab? Are we asking to much of the system? Are we not using the tags correctly?

The thing is, that you select for which branch the tag will be created, so I thought that the data would be available, but I guess not?