Creating a new feature using GITFLOW, it's natural to try and create a feature (for example) with spaces.

Fix For Broken Ethernet Support

Sourcetree hapilly accepts this, and then GIT rejects it. It would be really nice if you didn't get that far to have obscure and unfriendly GIT messages thrown back as a result of this rookie mistake.

If illegal characters are entered, the user should be notified and not allowed to create the GitFlow feature.

Guessing there are other places in the client where the also a problem.