I included a lot of other changes and fixes in the original MR (https://git.xfel.eu/gitlab/detectors/pycalibration/merge_requests/411) before figuring out how to get the checks to run only on changed files, which meant that the MR implementing pre-commit checks also refactored a decent chunk of code. It would be better to do that refactoring in separate MRs so I've closed the original one and opened this to replace it.
Don't mutate the code during pre-commit checks - changed my mind about this a few times, left it to mutate the code as that is only done on staged files, so any mutations can be reverted by undoing changes anyway. Added an explanation on this to the readme instead.
Add info to the readme and to the wiki
Add explanation of what each of the checks is for in more detail
Add scripts to execute w/ diff-only (same as the CI pipeline)
