Thanks. There are some pre-commit issues due to whitespace. Check the pre-commit check for the diff. Also, I think you need to git pull upstream manual-2.3.x to fix the rstcheck issues.

But the pre-commit errors don't seem related to my changes but to a Hercules controller.
What rstcheck?
I haven't cloned the repo locally.

But the pre-commit errors don't seem related to my changes but to a Hercules controller.
What rstcheck?

One of the pre-commit hooks that checks if the RST markup is valid.

I haven't cloned the repo locally.

Please do an pull the lastest manual-2.3.x branch from upstream into this branch.

Sounds complicated. What do you want me to achieve?

It actually isn't. Just open a shell and run the following commands:

git clone git@github.com:fkbreitl/manual.git mixxx-manual
cd mixxx-manual
git remote add upstream https://github.com/mixxxdj/manual.git
git checkout pioneer-ddj-200
git pull upstream manual-2.3.x

Then commit the merge and run:

git push origin pioneer-ddj-200

Ok, I did it. There are no pre-commit issues.
Why was git pull upstream manual-2.3.x necessary?
Did I fork from the wrong branch or repo?

No, there was a issue present in the upstream branch when you forked. It was fixed upstream in the meantime, but the fix was not part of this branch. By pulling in the changes, we can now review this properly and know that this branch is pre-commit warning-free.

Does it make sense to delete this repo and fork it from mixxxdj/manual in case of new contributions?

No, you can keep it. If you want to make a new contribution, I suggest to use the upstream remote as basis in any case:

If you don't have it (you can check with git remote -v):

git remote add upstream https://github.com/mixxxdj/manual.git

Next time you want to contribute, you can just do:

git fetch upstream
git checkout -b mybranch upstream/2.3

Alright. Thank you!