image_tag adds strange dot after file names on windows

On Windows, File#exist?("example.txt.") returns true, if example.txt exists (note the dot at the end). Because of that, methods like image_tag add a dot at the end of the file name.

Fix:

Change actionpack/lib/action_view/helpers/asset_tag_helper.rb:477 from:

              source += ".#{ext}" if ext && File.extname(source).blank? || File.exist?(File.join(ASSETS_DIR, dir, "#{source}.#{ext}"))

to:

              source += ".#{ext}" if ext && (File.extname(source).blank? || File.exist?(File.join(ASSETS_DIR, dir, "#{source}.#{ext}")))

Lots of assertions failed because of this in my app when I migrated from 1.2.6 to 2.1.0