Customers were surprised by the previous behavior, which destroyed branches even though an open merge request existed for it. Closes #29427
Rails by default use autoload for all dirs from app folder. require_relative not needed. See ActiveSupport::Dependencies.autoload_paths
It adds a button to the branches page that the user can use to delete all the branches that are already merged. This can be used to clean up all the branches that were forgotten to delete while merging MRs. Fixes #21076.
