Returns (git like) *diff*, as plain text. Shows changes introduced by
        ``rev2`` since ``rev1``.

        :param rev1: Entry point from which diff is shown. Can be
          ``self.EMPTY_CHANGESET`` - in this case, patch showing all
          the changes since empty state of the repository until ``rev2``
        :param rev2: Until which revision changes should be shown.
        :param ignore_whitespace: If set to ``True``, would not show whitespace
          changes. Defaults to ``False``.
        :param context: How many lines before/after changed lines should be
          shown. Defaults to ``3``.

def get_diff(self, rev1, rev2, path=None, ignore_whitespace=False,
                 context=3):
        """
        Returns (git like) *diff*, as plain text. Shows changes introduced by
        ``rev2`` since ``rev1``.

        :param rev1: Entry point from which diff is shown. Can be
          ``self.EMPTY_CHANGESET`` - in this case, patch showing all
          the changes since empty state of the repository until ``rev2``
        :param rev2: Until which revision changes should be shown.
        :param ignore_whitespace: If set to ``True``, would not show whitespace
          changes. Defaults to ``False``.
        :param context: How many lines before/after changed lines should be
          shown. Defaults to ``3``.
        """
        flags = ['-U%s' % context, '--full-index', '--binary', '-p', '-M', '--abbrev=40']
        if ignore_whitespace:
            flags.append('-w')

        if hasattr(rev1, 'raw_id'):
            rev1 = getattr(rev1, 'raw_id')

        if hasattr(rev2, 'raw_id'):
            rev2 = getattr(rev2, 'raw_id')

        if rev1 == self.EMPTY_CHANGESET:
            rev2 = self.get_changeset(rev2).raw_id
            cmd = ' '.join(['show'] + flags + [rev2])
        else:
            rev1 = self.get_changeset(rev1).raw_id
            rev2 = self.get_changeset(rev2).raw_id
            cmd = ' '.join(['diff'] + flags + [rev1, rev2])

        if path:
            cmd += ' -- "%s"' % path

        stdout, stderr = self.run_git_command(cmd)
        # If we used 'show' command, strip first few lines (until actual diff
        # starts)
        if rev1 == self.EMPTY_CHANGESET:
            lines = stdout.splitlines()
            x = 0
            for line in lines:
                if line.startswith('diff'):
                    break
                x += 1
            # Append new line just like 'diff' command do
            stdout = '\n'.join(lines[x:]) + '\n'
        return stdout