Do not check out new branch when loading cached results during runtime

[schmoelder]

When loading cached results at runtime, the output repo tries checking out a new branch if it does yet not exist locally. However, this causes the run to fail because other files might already be present in the output repo.

CADET-RDM/cadetrdm/repositories.py

Line 1371 in d5845e8

self.output_repo.checkout(branch_name)

Instead, use something like the following:

if branch_name not in local_branches:
    self.output_repo._git.create_head(
        branch_name
    )

Note, this is just quick-and-dirty fix. It would be better to add a method to our GitRepo class which wraps git.Repo.