pathmap_partial (String)

         # File lib/rake.rb, line 98
     98:     def pathmap_partial(n)
     99:       target = File.dirname(self)
    100:       dirs = target.pathmap_explode
    101:       if n > 0
    102:         File.join(dirs[0...n])
    103:       elsif n < 0
    104:         partial = dirs[n..-1]
    105:         if partial.nil? || partial.empty?
    106:           target
    107:         else
    108:           File.join(partial)
    109:         end
    110:       else
    111:         "."
    112:       end
    113:     end