0.10.5: bug fix release: print an error in case of duplicate groups and fixes an
        error in the permission check

0.10.3: bug fix release: trac permissions are no more cleared before insertion

0.10.2: bug fix release:
        - group definitions can now be placed anywhere
        - #trac special comments are correctly handled

0.10.0: --trac enables special commands to manage trac
        (http://trac.edgewall.org/) permissions.

0.9.17: @ and . are allowed in user names, no longer crashes when a
        user is memeber of more than one group

0.9.5:  -s subtree to specify that the svnaccess file is partial

0.9.4:  -u user to specify a user that has to retain write permissions
        to the root of the repository
