I am unable to use GitLab Mattermost with the iOS Mattermost APP.
Summary
When trying to use GitLab Mattermost, I am unable to sign in or use the iOS mobile app from http://about.mattermost.com/downloads/
Steps to reproduce
Set up a clean install of GitLab and enable Mattermost in the gitlab.rb file. Make sure you have a valid SSL in place and then try to log in to your Mattermost instance using the iOS app. When you click 'Sign in with GitLab' you are directed to a browser page on the phone to log in to your GitLab instance. After you log in, you remain in a web browser and are never taken back to the actual iOS app to use it...
Expected behavior
I expect to be able to sign in with GitLab and use the Mattermost app as shown in your own screenshot on your site...
https://gitlab.com/gitlab-org/gitlab-mattermost
Observed behavior
I wasn't able to use the Mattermost iOS app. I was stuck in a mobile web browser page and I am never taken back to the app.
Possible fixes
Not sure why this doesn't work. It looks like it should work right out of the box and apparently there was an issue closed that should have fixed this, yet it still doesn't work: