Pathname#relative_path_from uses is_a?

I reconsidered because simpler code would have better maintainablity.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66431 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/pathname/lib/pathname.rb

@@ -503,13 +503,9 @@ def each_child(with_directory=true, &b)
   # ArgumentError is raised when it cannot find a relative path.
   #
   def relative_path_from(base_directory)
+    base_directory = Pathname.new(base_directory) unless base_directory.is_a? Pathname
     dest_directory = self.cleanpath.to_s
-    base_directory =
-      if base_directory.respond_to? :cleanpath
-        base_directory
-      else
-        Pathname.new(base_directory)
-      end.cleanpath.to_s
+    base_directory = base_directory.cleanpath.to_s
     dest_prefix = dest_directory
     dest_names = []
     while r = chop_basename(dest_prefix)

test/pathname/test_pathname.rb

@@ -1439,6 +1439,7 @@ def test_relative_path_from_mock
       Pathname.new("/foo/bar").relative_path_from("/foo/baz"))
     obj = Object.new
     def obj.cleanpath() Pathname.new("/foo/baz") end
+    def obj.is_a?(m) m == Pathname end
     assert_equal(
       Pathname.new("../bar"),
       Pathname.new("/foo/bar").relative_path_from(obj))