Document exclude regex is on relative path

[polarathene]

I was using the -dry-run option which outputs absolute paths, and wondering why my config exclude was having trouble filtering out a top level directory...

Turned out that it's not applying regex based on the absolute path the dry run outputs, but relative paths from where the command is run? That should be documented imo 😅

[mstruebing]

Thank you very much for that issue.
Feel free to provide a pull request regarding that documentation changes, that would be great 👍