fun describe(dirty: Boolean, trimLeading: Boolean): String
Overrides Describer.describe
dirty - if this is true, the revision number is appended with "-dirty",
when there are uncommitted changes in the repository.
trimLeading - true, if the version number has the leading r stripped
IOException - if the process of svn info is not executed successfully within 2 minutes,
or if the result does not contain a revision.
Return
the SVN revision in the format "r123"