Merge pull request #846 from vladshablinsky/pinned_not_eligible

formula: pinned keg is not eligible for cleanup

Library/Homebrew/formula.rb

@@ -1611,6 +1611,8 @@ class Formula
         eligible_kegs.each do |keg|
           if keg.linked?
             opoo "Skipping (old) #{keg} due to it being linked"
+          elsif pinned? && keg == Keg.new(@pin.path.resolved_path)
+            opoo "Skipping (old) #{keg} due to it being pinned"
           else
             eligible_for_cleanup << keg
           end