Adding version detection to sf.net /download urls

SourceForge links can end with /download which appears to be part of
what is used to drive mirror selection. Modifying the version detection
extension of pathname.rb to detect this case for both sourceforge.net
and sf.net download selections.

This is sufficient for version detection but may not be sufficient for
other uses of /download links. I have not found any problems with links
that use /download, though.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Library/Homebrew/extend/pathname.rb

@@ -105,7 +105,12 @@ class Pathname
       # directories don't have extnames
       stem=basename.to_s
     else
-      stem=self.stem
+      # sourceforge /download
+      if %r[((?:sourceforge.net|sf.net)/.*)/download$].match to_s
+        stem=Pathname.new(dirname).stem
+      else
+        stem=self.stem
+      end
     end
 
     # github tarballs, like v1.2.3

Library/Homebrew/test/test_versions.rb

@@ -98,6 +98,11 @@ class VersionTests < Test::Unit::TestCase
     check "http://example.com/foo_bar-1.21.tar.gz", '1.21'
   end
 
+  def test_version_sourceforge_download
+    check "http://sourceforge.net/foo_bar-1.21.tar.gz/download", '1.21'
+    check "http://sf.net/foo_bar-1.21.tar.gz/download", '1.21'
+  end
+
   def test_version_github
     check "http://github.com/lloyd/yajl/tarball/1.0.5", '1.0.5'
   end