Yes, I do have my files in the git repo. Although I have not quite understood which part it takes from the remote git repo, and which part it takes from my local system.

it will do "git pull" on the remote machine and then apply any uncommitted changes it has stored in the Task

It seems that one also needs to explicitly hand in the git repo in the pipeline and task definitions via PipelineController,

Correct, unless the pipeline logic and the steps are the same git repo, you can verify that if you click on the detials of each step and check what is listed under the repo section in the execution tab

And a second thing: When starting a pipeline, it seems that ClearML would take my local virtual environment and extract its dependencies from that, independent of the requirements.txt

Correct, if you want to disable this behaviour set pass " packages=False " to the decorator and the agent will default to the packages in your git repo