When creating a duplicate fork an unclear error message is displayed.

Summary

When a project is attempted to be re-forked with the same name, an unclear error message is displayed.

This issue was part of the 2021-05-03 In some scenarios users receive errors for forking projects production incident.

The fork_project_form feature flag was disabled in production, and then the behaviour is the project cannot be re-forked, and it is not possible to specify a new fork name. Attempting to re-fork takes the user to the existing fork.

Steps to reproduce

Fork a project into a user namespace, eg: https://gitlab.com/gitlab-com/runbooks
Fork the project a second time, error message is displayed but it is not clear what the error is
It is possible to fork the project with a new name

Example Project

https://gitlab.com/sean_carroll/runbooks-new-2

What is the current bug behavior?

Unclear error 409. Please see screenshots below.

What is the expected correct behavior?

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info


(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)