I have a repo that I would like to branch, say into b1 b2. It contains a file main.py that imports imported.py. Therefore, when I change imported.py, I would like the most uptodate version to be available to both b1 and b2. I thought it might be best to create a separate git repository repo A that contains main.py and then another repo B for imported.py... but what is the standard (and preferably simple) protocol for such a situation?