Custom PullEventHandler lost when saving Git Project Settings

[copperschnack]

Steps to reproduce:

• Specify custom pull event class extending SourceControl.Git.PullEventHandler.Default w/ some write output in OnPull() during
  d ##class(SourceControl.Git.API).Configure()

• Pull change from git upstream to verify that the output is shown

• Open Git > Settings and save

• Pull other change from git upstream - custom pull handler is no longer in place

[isc-tleavitt]

@copperschnack good find, thanks for reporting this.

[isc-tleavitt]

Solution: Settings UI needs to dynamically populate the dropdown based on existing subclasses of SourceControl.Git.PullEventHandler (see %Dictionary.ClassDefinition:SubclassOf) rather than being hardcoded to the two we ship.