<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=498552) </details> <!--IssueSummary end--> context: https://gitlab.com/gitlab-org/gitlab/-/issues/444302#note_2115369031 update to keep the modal open while we validate branch name. currently the validation is done in [blob controller](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/controllers/projects/blob_controller.rb), we can add a call to graphql endpoint, to validate if: - the entered name is valid - [already exists ](https://gitlab.com/gitlab-org/gitlab/-/issues/444302#note_2159015811)