Switching branch using the dropdown in the repo-view gives 404-page when branch name contains swedish letter å

Summary

Switching branch by selecting one in the dropdown in the repo page in a project landed me on a 404-page. Most likely because the branch-name contained the Swedish letter å which got url-encoded, like so https://mygitlab.com/victor/my-project/refs/switch?utf8=%E2%9C%93&destination=tree&path=&ref=avg%25E5ngar. Un-encoding the å to https://mygitlab.com/victor/my-project/refs/switch?utf8=✓&destination=tree&path=&ref=avgångar lands me on the expected page.

Steps to reproduce

1. Push a branch with å in the name, like avgångar. (But I'm guessing any non-english characters might be affected)
2. Select the branch from the dropdown in the repo view in the project
3. Land on a 404-page

Expected behavior

Land on the tree page for given branch, in this case it would be https://mygitlab.com/victor/my-project/tree/avgångar

Actual behavior

Land on a 404-page

Output of checks

Don't have ssh to that machine handy atm. But version info from dashboard.

GitLab 8.12.7
GitLab Shell 3.6.1
GitLab Workhorse 0.8.2
GitLab API v3
Git 2.7.4
Ruby 2.3.1p112
Rails 4.2.7.1
PostgreSQL 9.2.18

Status changed to closed

@victorhaggqvist Thank you for the bug report! 👍 I am closing this in favor of #21248 (closed).

Status changed to closed

Added frontend ~12980 reproduced on GitLab.com labels