'Update listwidgets from the combobox selection
Update either the left or right listwidgets
to reflect the available items.'

def update_combo_boxes(self, left=False):

    if left:
        which = self.left_combo.currentText()
        widget = self.left_list
    else:
        which = self.right_combo.currentText()
        widget = self.right_list
    if (not which):
        return
    if (which == self.LOCAL):
        new_list = ([self.SANDBOX] + self.local_branches)
    else:
        new_list = ([self.BRANCH_POINT] + self.remote_branches)
    widget.clear()
    widget.addItems(new_list)
    if new_list:
        item = widget.item(0)
        widget.setCurrentItem(item)
        item.setSelected(True)
