line = next(diff_lines)

            while old_line < old_end or new_line < new_end:

                if not line:

                    raise Exception('error parsing diff - empty line at -%s+%s' % (old_line, new_line))

                affects_old = affects_new = False

                command = line[0]

                if command == '+':

                    affects_new = True

                    action = 'add'

                    added += 1

                elif command == '-':

                    affects_old = True

                    action = 'del'

                    deleted += 1

                elif command == ' ':

                    affects_old = affects_new = True

                    action = 'unmod'

                else:

                    raise Exception('error parsing diff - unknown command in line %r at -%s+%s' % (line, old_line, new_line))

                    old_line += affects_old

                    new_line += affects_new

                    lines.append({

                        'old_lineno':   affects_old and old_line or '',

                        'new_lineno':   affects_new and new_line or '',

                        'action':       action,

                        'line':         line[1:],

                    })

                line = next(diff_lines)

                if _newline_marker.match(line):

                    # we need to append to lines, since this is not

                    # counted in the line specs of diff

                    lines.append({

                        'old_lineno':   '',

                        'new_lineno':   '',

                        'action':       'context',

                        'line':         line,

                    })

                    line = next(diff_lines)

            if old_line > old_end:

                raise Exception('error parsing diff - more than %s "-" lines at -%s+%s' % (old_end, old_line, new_line))

            if new_line > new_end: