git-deps web UI server route doesn't seem to handle slashes correctly

At the company where I work, we use some conventions around branch names, including prefixing feature branches with `feat/` and bugfix branches with `fix/`. When I feed one of those into the UI's input and submit, a request is sent to the server and answered with a 404 code.

Despite their similarity, that probably isn't a duplicate of #74, as 422 is the code sent when the server actually receives and treats the request, but the requested commit-ish isn't found. I couldn't find any related issues.

Does anyone get the same behavior? I'm using it under Ubuntu 16.04 and Python 3.5.2.

Reproduce the UI request with a branch name such as feat/… or fix/… and compare it with a commit-ish that returns 422. Trace the web UI server route handling the submitted branch name; done means slash-containing branch names reach the server and return the expected response instead of 404.

Written by the indexing model from the issue text.