def generate_control_field(self, revision=None):
value = "<STR_LIT>" % (self.remote or self.local, self.find_revision_id(revision))<EOL>return self.control_field, value<EOL>
Generate a Debian control file field referring for this repository and revision.

:param revision: A reference to a revision, most likely the name of a
                 branch (a string, defaults to :attr:`default_revision`).
:returns: A tuple with two strings: The name of the field and the value.

This generates a `Vcs-Bzr` field for Bazaar repositories, a `Vcs-Git`
field for Git repositories and a `Vcs-Hg` field for Mercurial
repositories. Here's an example based on the public git repository of
the `vcs-repo-mgr` project:

>>> from vcs_repo_mgr import coerce_repository
>>> repository = coerce_repository('https://github.com/xolox/python-vcs-repo-mgr.git')
>>> repository.generate_control_field()
('Vcs-Git', 'https://github.com/xolox/python-vcs-repo-mgr.git#b617731b6c0ca746665f597d2f24b8814b137ebc')