### Summary When creating a second merge request using the same source/target branch combination results in error >The form contains the following error: Validate branches Cannot Create: This merge request already exists: ### Steps to reproduce * Create a branch - initial-branch * Create a merge request using initial-branch to master * Create a merge request using initial-branch to master * On submit - error results ### What is the current *bug* behavior? An error is displayed >The form contains the following error: Validate branches Cannot Create: This merge request already exists: merge request is not created. ### What is the expected *correct* behavior? Merge request to be created ### Relevant logs and/or screenshots gdk errors out as 500 after making gitaly calls, no errors seen in other logs or developer web console. ### Output of checks Also happens on GitLab.com and older versions. #### Results of GitLab environment info <details> <summary>Expand for output related to GitLab environment info</summary> <pre> System information System: Ubuntu 16.04 Proxy: no Current User: git Using RVM: no Ruby Version: 2.3.5p376 Gem Version: 2.6.13 Bundler Version:1.13.7 Rake Version: 12.1.0 Redis Version: 3.2.5 Git Version: 2.13.6 Sidekiq Version:5.0.4 Go Version: unknown GitLab information Version: 10.1.2-ee Revision: 9937019 Directory: /opt/gitlab/embedded/service/gitlab-rails DB Adapter: postgresql DB Version: 9.6.5 URL: http://astrachan-latest HTTP Clone URL: http://astrachan-latest/some-group/some-project.git SSH Clone URL: git@astrachan-latest:some-group/some-project.git Elasticsearch: no Geo: no Using LDAP: no Using Omniauth: no GitLab Shell Version: 5.9.3 Repository storage paths: - default: /var/opt/gitlab/git-data/repositories Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks Git: /opt/gitlab/embedded/bin/git </pre> </details> #### Results of GitLab application Check <details> <summary>Expand for output related to the GitLab application check</summary> <pre> root@astrachan-latest:~# sudo gitlab-rake gitlab:check SANITIZE=true Checking GitLab Shell ... GitLab Shell version >= 5.9.3 ? ... OK (5.9.3) Repo base directory exists? default... yes Repo storage directories are symlinks? default... no Repo paths owned by git:root, or git:git? default... yes Repo paths access is drwxrws---? default... yes hooks directories in repos are links: ... 2/1 ... ok 3/2 ... ok 9/3 ... ok 6/4 ... ok 6/5 ... ok 3/6 ... ok 6/7 ... repository is empty 6/8 ... repository is empty 6/9 ... repository is empty 6/10 ... ok 6/11 ... repository is empty 6/12 ... repository is empty 1/13 ... ok 1/14 ... ok Running /opt/gitlab/embedded/service/gitlab-shell/bin/check Check GitLab API access: OK Redis available via internal API: OK Access to /var/opt/gitlab/.ssh/authorized_keys: OK gitlab-shell self-check successful Checking GitLab Shell ... Finished Checking Sidekiq ... Running? ... yes Number of Sidekiq processes ... 1 Checking Sidekiq ... Finished Reply by email is disabled in config/gitlab.yml Checking LDAP ... LDAP is disabled in config/gitlab.yml Checking LDAP ... Finished Checking GitLab ... Git configured correctly? ... yes Database config exists? ... yes All migrations up? ... yes Database contains orphaned GroupMembers? ... no GitLab config exists? ... yes GitLab config up to date? ... yes Log directory writable? ... yes Tmp directory writable? ... yes Uploads directory exists? ... yes Uploads directory has correct permissions? ... yes Uploads directory tmp has correct permissions? ... yes Init script exists? ... skipped (omnibus-gitlab has no init script) Init script up-to-date? ... skipped (omnibus-gitlab has no init script) Projects have namespace: ... 2/1 ... yes ... 1/14 ... yes Redis version >= 2.8.0? ... yes Ruby version >= 2.3.3 ? ... yes (2.3.5) Git version >= 2.7.3 ? ... yes (2.13.6) Git user has default SSH configuration? ... yes Active users: ... 6 Elasticsearch version 5.1 - 5.5? ... skipped (elasticsearch is disabled) Checking GitLab ... Finished (we will only investigate if the tests are passing) </pre> </details> ### Possible fixes Error happens after click 'Submit Merge Request'