def get_revision():
package_dir = os.path.dirname(__file__)<EOL>checkout_dir = os.path.normpath(os.path.join(package_dir, '<STR_LIT:..>'))<EOL>path = os.path.join(checkout_dir, '<STR_LIT>')<EOL>if os.path.exists(path):<EOL><INDENT>return _get_git_revision(path)<EOL><DEDENT>return None<EOL>
:returns: Revision number of this branch/checkout, if available. None if
    no revision number can be determined.