Git on Windows does not properly handle symlinks (this can be seen in different issues, where only a file containing the name to the link target is reported).
This makes the Vim plugin probably not work as expected, where different filetypes link to the "html" directory.
The solution might be to not use the ftplugin mechanism, but provide a autocmd FileType ... mechanism instead, which would load the plugin?!
autocmd FileType ...
Add support for `smarty` filetype (PHP template language)
@MarcWeber did something about it already: https://github.com/MarcWeber/sparkup/blob/master/vim/plugin/sparkup.vim
@rstacruz: The autocmd idea seems sane to me; should I prepare a Pull Request? Sparkup already offers <Tab> for navigating to the next empty tag, so that's not a concern. But if the augroup fixes shortcut problems for Windows users, maybe it should be switched.