Summary: When selecting a Github repo to base a multibranch pipeline off of, if there are too many repos available to the Github user, the drop down menu fails to load and shows a 504 error. This was specifically identified when tested against 5000 repos.
Steps to reproduce. 1. Have a Github account with access to 5000 repos. 2. Create a new multibranch pipeline job. 3. Select the appropriate credentials. 4. Click the Repository drop down menu. 5. After a while, the 504 message will display and the drop down remains empty
Expected behavior: The full list of repos would display, or an adequate way of searching through the repos would be available.
Actual behavior: No repos are displayed and a 504 error shows up. (See screenshot above)
Workaround: Using a script to create the job and set the repository.