if name not in self.tags:

            raise TagDoesNotExistError("Tag %s does not exist" % name)

        if message is None:

            message = "Removed tag %s" % name

        if date is None:

            date = datetime.datetime.now().strftime('%a, %d %b %Y %H:%M:%S')

        local = False

        try:

            tag(self._repo, name, nullid, message, local, user, date)

            self.tags = self._get_tags()

        except Abort as e:

            raise RepositoryError(e.message)

    @LazyProperty

    def bookmarks(self):

        """

        Gets bookmarks for this repository

        """

        return self._get_bookmarks()

    def _get_bookmarks(self):

        if self._empty:

            return {}

        sortkey = lambda ctx: ctx[0]  # sort by name

        _bookmarks = [(safe_unicode(n), hex(h),) for n, h in

                 self._repo._bookmarks.items()]

        return OrderedDict(sorted(_bookmarks, key=sortkey, reverse=True))

    def _get_all_revisions(self):

        return [self._repo[x].hex() for x in self._repo.filtered('visible').changelog.revs()]

    def get_diff(self, rev1, rev2, path='', 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``. If negative value is passed-in, it will be

          set to ``0`` instead.

        """

        # Negative context values make no sense, and will result in

        # errors. Ensure this does not happen.

        if context < 0:

            context = 0

        if hasattr(rev1, 'raw_id'):

            rev1 = getattr(rev1, 'raw_id')

        if hasattr(rev2, 'raw_id'):

            rev2 = getattr(rev2, 'raw_id')

        # Check if given revisions are present at repository (may raise

        # ChangesetDoesNotExistError)

        if rev1 != self.EMPTY_CHANGESET:

            self.get_changeset(rev1)

        self.get_changeset(rev2)

        if path:

            file_filter = match(self.path, '', [path], exact=True)

        else:

            file_filter = None

        return ''.join(patch.diff(self._repo, rev1, rev2, match=file_filter,

                          opts=diffopts(git=True,

                                        showfunc=True,

                                        ignorews=ignore_whitespace,

                                        context=context)))

    @classmethod

    def _check_url(cls, url, repoui=None):

        """

        Function will check given url and try to verify if it's a valid

        link. Sometimes it may happened that mercurial will issue basic

        auth request that can cause whole API to hang when used from python

        or other external calls.

        On failures it'll raise urllib2.HTTPError, exception is also thrown

        when the return code is non 200

        """

        # check first if it's not an local url

        if os.path.isdir(url) or url.startswith('file:'):

            return True

        if url.startswith('ssh:'):

            # in case of invalid uri or authentication issues, sshpeer will

            # throw an exception.

            return True

        url_prefix = None

        if '+' in url[:url.find('://')]:

            url_prefix, url = url.split('+', 1)

        handlers = []

        url_obj = hg_url(url)

        test_uri, authinfo = url_obj.authinfo()

        url_obj.passwd = '*****'

        cleaned_uri = str(url_obj)

        if authinfo:

            # create a password manager

            passmgr = urllib2.HTTPPasswordMgrWithDefaultRealm()

            passmgr.add_password(*authinfo)

            handlers.extend((httpbasicauthhandler(passmgr),

                             httpdigestauthhandler(passmgr)))

        o = urllib2.build_opener(*handlers)

        o.addheaders = [('Content-Type', 'application/mercurial-0.1'),

                        ('Accept', 'application/mercurial-0.1')]

        q = {"cmd": 'between'}

        q.update({'pairs': "%s-%s" % ('0' * 40, '0' * 40)})

        qs = '?%s' % urllib.urlencode(q)

        cu = "%s%s" % (test_uri, qs)

        req = urllib2.Request(cu, None, {})

        try:

            resp = o.open(req)

            if resp.code != 200:

                raise Exception('Return Code is not 200')

        except Exception as e:

            # means it cannot be cloned

            raise urllib2.URLError("[%s] org_exc: %s" % (cleaned_uri, e))

        if not url_prefix: # skip svn+http://... (and git+... too)

            # now check if it's a proper hg repo

            try:

            except Exception as e:

                raise urllib2.URLError(

                    "url [%s] does not look like an hg repo org_exc: %s"

                    % (cleaned_uri, e))

        return True

    def _get_repo(self, create, src_url=None, update_after_clone=False):

        """

        Function will check for mercurial repository in given path and return

        a localrepo object. If there is no repository in that path it will

        raise an exception unless ``create`` parameter is set to True - in

        that case repository would be created and returned.

        If ``src_url`` is given, would try to clone repository from the

        location at given clone_point. Additionally it'll make update to

        working copy accordingly to ``update_after_clone`` flag

        """

        try:

            if src_url:

                url = safe_str(self._get_url(src_url))

                opts = {}

                if not update_after_clone:

                    opts.update({'noupdate': True})

                MercurialRepository._check_url(url, self.baseui)

                clone(self.baseui, url, self.path, **opts)

                # Don't try to create if we've already cloned repo

                create = False

            return localrepo.instance(self.baseui, self.path, create=create)

        except (Abort, RepoError) as err:

            if create:

                msg = "Cannot create repository at %s. Original error was %s" \

                    % (self.path, err)

            else:

                msg = "Not valid repository at %s. Original error was %s" \

                    % (self.path, err)

            raise RepositoryError(msg)

    @LazyProperty

    def in_memory_changeset(self):

        return MercurialInMemoryChangeset(self)

    @LazyProperty

    def description(self):

        undefined_description = u'unknown'

        _desc = self._repo.ui.config('web', 'description', None, untrusted=True)

        return safe_unicode(_desc or undefined_description)

    @LazyProperty

    def contact(self):

        undefined_contact = u'Unknown'

        return safe_unicode(get_contact(self._repo.ui.config)

                            or undefined_contact)

    @LazyProperty

    def last_change(self):

        """

        Returns last change made on this repository as datetime object

        """

        return date_fromtimestamp(self._get_mtime(), makedate()[1])

    def _get_mtime(self):

        try:

            return time.mktime(self.get_changeset().date.timetuple())

        except RepositoryError:

            # fallback to filesystem

            cl_path = os.path.join(self.path, '.hg', "00changelog.i")

            st_path = os.path.join(self.path, '.hg', "store")

            if os.path.exists(cl_path):

                return os.stat(cl_path).st_mtime

            else:

                return os.stat(st_path).st_mtime

    def _get_revision(self, revision):

        """

        Gets an ID revision given as str. This will always return a full

        40 char revision number

        :param revision: str or int or None

        """

        if isinstance(revision, unicode):

            revision = safe_str(revision)

        if self._empty:

            raise EmptyRepositoryError("There are no changesets yet")

        if revision in [-1, None]:

            revision = 'tip'

        try:

            if isinstance(revision, int):

                return self._repo[revision].hex()

            try:

                return scmutil.revsymbol(self._repo, revision).hex()

            except AttributeError: # revsymbol was introduced in Mercurial 4.6

"""

Mercurial libs compatibility

"""

import mercurial

from mercurial import demandimport

# patch demandimport, due to bug in mercurial when it always triggers demandimport.enable()

demandimport.enable = lambda *args, **kwargs: 1

from mercurial import archival, merge as hg_merge, patch, ui

from mercurial import discovery

from mercurial import localrepo

from mercurial import unionrepo

from mercurial import scmutil

from mercurial import config

from mercurial import tags as tagsmod

from mercurial.commands import clone, nullid, pull

from mercurial.context import memctx, memfilectx

from mercurial.error import RepoError, RepoLookupError, Abort

from mercurial.hgweb import hgweb_mod

from mercurial.hgweb.common import get_contact

from mercurial.match import match

from mercurial.mdiff import diffopts

from mercurial.node import hex

from mercurial.encoding import tolocal

from mercurial.discovery import findcommonoutgoing

from mercurial.hg import peer

from mercurial.util import url as hg_url

from mercurial.scmutil import revrange

from mercurial.node import nullrev

from mercurial.url import httpbasicauthhandler, httpdigestauthhandler

# Mercurial 4.5 8a0cac20a1ad introduced an extra memctx changectx argument

# - introduce an optional wrapper factory that doesn't pass it on

import inspect

if inspect.getargspec(memfilectx.__init__).args[2] != 'changectx':

    __org_memfilectx = memfilectx

    memfilectx = lambda repo, changectx, *args, **kwargs: __org_memfilectx(repo, *args, **kwargs)

# workaround for 3.3 94ac64bcf6fe and not calling largefiles reposetup correctly

localrepo.localrepository._lfstatuswriters = [lambda *msg, **opts: None]

# 3.5 7699d3212994 added the invariant that repo.lfstatus must exist before hitting overridearchive

localrepo.localrepository.lfstatus = False

# Mercurial 4.2 moved tag from localrepo to the tags module

def tag(repo, *args):

    try:

        tag_f  = tagsmod.tag

    except AttributeError:

        return repo.tag(*args)

    tag_f(repo, *args)