Updating local copies of repos

### Context
One of the scripts [src/github_repo_request_local.py](https://github.com/commercetest/nlnet/blob/main/src/github_repo_request_local.py) clones repos from github.com which then facilitates local analysis.

Eventually/soon we'll want to track the changes in the codebases particularly in terms of their approach to software testing. For this we may want to update the code in the local instance based on the changes that have occurred since we previously cloned it. Thankfully `git` automatically records the history of each instance of a repo and provides mechanisms to perform updates.

### Additional thoughts
TBD how sophisticated our analysis needs to be and how much our scripts would want/need to take account of structural and naming changes to the remote repo. For example, if they rename the trunk from `master` to `main`? if they use `develop` as their primary trunk branch, if they rename the repo, or even relocate it to another hosting provider. Commit hashes are probably sufficiently unique to provide a signature of a repo and/or we might decide that scrapping historical data for a repo is more expedient and sufficient for the purposes of our analysis.

Start by reading src/github_repo_request_local.py and trace how repositories are cloned and recorded locally. Define the supported update behavior and repository-change cases before implementing it; done means local copies reflect subsequent remote changes in a way that supports the existing analysis.

Written by the indexing model from the issue text.