Branch name rules should be enforced instead of erring out

Version

0.20.4

Operating System

Linux

Distribution Method

deb (Linux)

Describe the issue

There are certain restrictions on how branches should be named enforced by Git. For now, the only one I can think of is that a branch name cannot have a trailing slash.

I think Butler should warn you about this, preventing you from ever naming the branch.

Currently, it simply errs out with a semi-cryptic error:

Of course, reading the error you can quite clearly tell what's happening and why Git is upset, but still, Butler should probably prevent you from ever doing this anyhow.

How to reproduce (Optional)

1. Make a branch ending in /
2. View error

Expected behavior (Optional)

I would expect Butler to stop me from doing this instead of dumping a git error log.