FileSystemRemoteRepoRef provides a set function for the branch property that sets this.opts.branch. There is a corresponding get function for branch as well. Unfortunately, super/AbstractRemoteRepoRef constructor sets the branch at a time when the opts property of FileSystemRemoteRepoRef has not been set yet, so you get a Cannot set property 'branch' of undefined error. Before, the branch property was not set by the AbstractRemoteRepoRef constructor, so this function/error was not triggered. The implementation of FileSystemRemoteRepoRef should not prohibit the parent class from setting the branch property.
FileSystemRemoteRepoRef provides a set function for the branch property that sets this.opts.branch. There is a corresponding get function for branch as well. Unfortunately, super/AbstractRemoteRepoRef constructor sets the branch at a time when the opts property of FileSystemRemoteRepoRef has not been set yet, so you get a
Cannot set property 'branch' of undefined error. Before, the branch property was not set by the AbstractRemoteRepoRef constructor, so this function/error was not triggered. The implementation of FileSystemRemoteRepoRef should not prohibit the parent class from setting the branch property.