Special character-containing filenames in Issuable Templates

Summary

Special character-containing filenames cause errors in the Issuable Templates (Issue Templates/Merge Request Templates) Web UI.

Steps to reproduce

  1. Add markdown files containing special characters including #, %, ?, . or ending with (white space) (confirmed with Firefox 58 for the latter) to .gitlab/issue_templates (or .gitlab/merge_request_templates) on the default branch by committing and pushing (or doing on Web UI).
  2. Have access to New Issue (or New Merge Request) to select any of the templates prepared as above from issuable templates.
  3. You'll get an error message like Something went wrong on our end. on top.

Example Project

You can use https://gitlab.com/tnir/tnir-gitlab-test-general/issues/new to reproduce the above.

What is the current bug behavior?

Templates are not applied with errors.

What is the expected correct behavior?

Templates with such characters should be applied like templates without such characters.

Relevant logs and/or screenshots

issuable-templates-bug

Output of checks

This bug happens on GitLab.com. (as of 2017-11-10 probably 10.1.2)

Possible fixes

I will create MRs for this soon.

/label ~bug ~"project templates"