I left a few comments on the tests. Otherwise, I quite like the patch series. Force-setting the extended attributes on visible-but-starting-with-a-dot files seems like a good compromise to fix the bug at hand without requiring a ton of attribute setting and I couldn't think of any better solution.
This won't fix the case of Wine-created dot files when the show_dot_files option is enabled if the user then disables the option, which again seems like a good compromise.