svn:external set and the output of 'svn status' returned the check for
the external. E.g.
$ svn st
X Application
Performing status on external item at 'Application'
Shouldn't be marked as being dirty. By grepping for only the valid
output for what should be class as dirty, it won't return false
positives.
If the svn plugin is used, svn info (repo name and wether the repo is dirty) is displayed in the prompt like with git. Just lke with git, the colors can be manipulated with variables (see awesomepanda theme for example).
