%-Characters in source branches for MR are changed

Summary

We add the issue number into the name of our feature branches, e.g. ''feature/#413_generic_behavior''

That worked fine so far. Now when I try to create a merge request for that branch I get the following error:

The form contains the following error:
Source branch "feature/%23413_generic_behavior" does not exist

And also the # sign in the pick drop-down menu is changed, see screenshot below

Steps to reproduce

create a branch with a # in the name and try to create a merge request

Relevant logs and/or screenshots

Before clicking:

After clicking:

GitLab Community Edition 10.8.0 55e4a0b3

Possible fixes

It currently still works, if I use the convenience function to create a MR for my last push Create Merge Request, instead of New Merge Request (there I can even use the change branches functionallity to change the target branch, but not the source branch)