Mirroring Repository with Pull creates a Push as well

Summary

When creating a pull mirror repository on a project, GitLab also creates a push mirror repository in Internet Explorer 11.

A customer reported this issue in GitLab 11.10.4, but we were able to reproduce this in 12.3.4.

The workaround is to simply delete the unwanted push repository that GitLab creates.

Steps to reproduce

See attached video of bug. Only happens in Internet Explorer 11

Video_MP4__1302x1160_

What is the expected correct behavior?

When a pull mirror is created, it SHOULD NOT create a push mirror as well

Relevant logs and/or screenshots

We compared the POST data sent to /<GROUP>/<PROJECT>/mirror and noticed that this is different on Internet Explorer 11. IE has an extra remote_mirrors_attributes in the POST data:

Chrome

Processing by Projects::MirrorsController#update as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"[FILTERED]", "url"=>"https://github.com/twbs/bootstrap.git", "mirror_direction"=>"pull", "project"=>{"mirror"=>"1", "username_only_import_url"=>"[FILTERED]", "only_mirror_protected_branches"=>"0", "import_data_attributes"=>{"ssh_known_hosts"=>"", "auth_method"=>"password", "password"=>"[FILTERED]"}, "mirror_user_id"=>"2", "mirror_overwrites_diverged_branches"=>"0", "mirror_trigger_builds"=>"0"}, "namespace_id"=>"anton", "project_id"=>"134360-pull-test"}

Internet Explorer 11

Processing by Projects::MirrorsController#update as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"[FILTERED]", "url"=>"https://github.com/twbs/bootstrap.git", "mirror_direction"=>"pull", "project"=>{"mirror"=>"1", "username_only_import_url"=>"[FILTERED]", "only_mirror_protected_branches"=>"0", "import_data_attributes"=>{"ssh_known_hosts"=>"", "auth_method"=>"password", "password"=>"[FILTERED]"}, "mirror_user_id"=>"2", "mirror_overwrites_diverged_branches"=>"0", "mirror_trigger_builds"=>"0", "remote_mirrors_attributes"=>{"0"=>{"enabled"=>"1", "url"=>"https://github.com/twbs/bootstrap.git", "only_protected_branches"=>"0", "ssh_known_hosts"=>"", "auth_method"=>"password", "password"=>"[FILTERED]"}}}, "namespace_id"=>"anton", "project_id"=>"134360-pull-test"}