middleware: move handling of permanent repo URLs to separate middleware This is about the handling of repo URLs like '_123' for the repo with repo_id 123. The de-mangling of such URLs was spread out across multiple layers. It fits much more nicely as a middleware layer. The code in routing and simplehg / simplegit can thus be removed. The base _get_by_id function was confusing - fix it by removing it. To do that, refactor utils introducing fix_repo_id_name to replace get_repo_by_id. We now assume in the application that we never have any extra leading '/' in URL paths. And while trailing extra '/' might be fine in actual URLs, they must be handled at the routing level, not propagated through all layers. This changeset is not really changing that.

pytest >= 3.3.0, < 3.8
pytest-runner < 4.3
pytest-sugar >= 0.7.0, < 0.10
pytest-benchmark < 3.2
pytest-localserver < 0.5
mock < 2.1
Sphinx < 1.8
WebTest < 2.1