Specify a validation workspace filter in a simple text format that each package workspace filter will be evaluated against.
Simple spec is defined simply as a line-by-line format where:
A package filter root is "covered" by a validation filter root if the package filter root path starts with, or is the same as the validation filter root path. Once the "covering" validation filter root is identified, the package filter root's include/exclude rules are inspected to be sure that they contain all of the validation filter's rules in order, at the end of the list.
For example, to require that packages exclude the /etc/packages folder:
        /etc                 # define /etc as the filter root
        -/etc/packages(/.)?  # exclude package paths