Resetting of assignment does not delete remaining files in the user directory

[meffmadd]

Describe the bug
When resetting the assignment in the assignment view, files that are present (e.g. old files that have been removed from the repo) are not deleted but stay in the directory.

To Reproduce
Steps to reproduce the behavior:

1. Add file to assignment and push.
2. Go to the assignment view and pull the release repo.
3. In the course manage view, delete the file from step 1 and add a new file.
4. Go to the assignment view and reset the assignment. Now 2 files are in the directory (from step 1 and step 3).

Expected behavior
Resetting the assignment should leave no extra files in the user directory and the user directory should contain exactly the files that are in the release repo.