In particular:
 * use def rather than assigning lambda function
 * unused imports
 * 'X not in Y' vs 'not X in Y'

An example of this is e.g. EUC-TW

In some cases, it seems to find an encoding that's not valid for the
entire string.

* Docker image: Fix ownership issue with Git 2.36+

* Update tests.yml

Add pyproject.toml.

Handle SymrefLoop. Fixes: #293

Support 'main' as a default branch name to try.

Fix InternalServerError when viewing history of a blob.

[ci skip]

This should fix exceptions with undefined newblob, when there's a submodule that's the first path in the tree.

This at least allows rendering pages rather than throwing 500s.