Steps to reproduce

1. Create a file with a colon : in the filename, e.g. Tue 27 Mar 2018 11:43:04 AEDT.txt
2. Edit the file online in Bitbucket Server
3. Upon save/commit, tick the 'Create pull request' checkbox
4. Click 'Create pull request'

Expected results

A branch is created based on the suggested branch name, and I get redirected to create the pull request.

Actual results

An error message is shown, saying the suggested branch name is invalid:

Basically, Bitbucket tries to help by suggesting a branch name, but it's not helping - as the branch name is invalid. Some string sanitation would be nice here.