pathname: make compute_disk_usage handle symlinks.

Library/Homebrew/extend/pathname.rb

@@ -26,11 +26,17 @@ module DiskUsageExtension
   private
 
   def compute_disk_usage
-    if directory?
+    path = if symlink?
+      resolved_path
+    else
+      self
+    end
+
+    if path.directory?
       scanned_files = Set.new
       @file_count = 0
       @disk_usage = 0
-      find do |f|
+      path.find do |f|
         if f.directory?
           @disk_usage += f.lstat.size
         else
@@ -47,7 +53,7 @@ module DiskUsageExtension
       end
     else
       @file_count = 1
-      @disk_usage = lstat.size
+      @disk_usage = path.lstat.size
     end
   end
 end