1377 - Blacklist dependencies in git

now ensure_dependencies.py add dependecies to .git/info/exclude. 
That's too much, actually. This *warning* will appear even if one uses Mercurial for both, the current and the sub-repository - although Mercurial ignores sub-directories with an `.hg` repo by default. Better would be something like `if !self.istype(target): logging.warning("...")` - which also allows for a more specific log message so one could also remove the comments above.