import django

import os.path

import re

def get_svn_revision(path=None):

    """

    Returns the SVN revision in the form SVN-XXXX,

    where XXXX is the revision number.

    Returns SVN-unknown if anything goes wrong, such as an unexpected

    format of internal SVN files.

    If path is provided, it should be a directory whose SVN info you want to

    inspect. If it's not provided, this will use the root django/ package

    directory.

    """

    rev = None

    if path is None:

        path = django.__path__[0]

    entries_path = '%s/.svn/entries' % path

    try:

        entries = open(entries_path, 'r').read()

    except IOError:

        pass

    else:

        # Versions >= 7 of the entries file are flat text.  The first line is

        # the version number. The next set of digits after 'dir' is the revision.

        if re.match('(\d+)', entries):

            rev_match = re.search('\d+\s+dir\s+(\d+)', entries)

            if rev_match:

                rev = rev_match.groups()[0]

        # Older XML versions of the file specify revision as an attribute of

        # the first entries node.

        else:

            from xml.dom import minidom

            dom = minidom.parse(entries_path)

            rev = dom.getElementsByTagName('entry')[0].getAttribute('revision')

    if rev:

        return u'SVN-%s' % rev

    return u'SVN-unknown'