should catch all the garbage that macs sprinkle onto flashdrives;
https://a.ocv.me/pub/stuff/?doc=appledoubles-and-friends.txt
will notice and suggest to skip the following files/dirs:
* __MACOSX
* .DS_Store
* .AppleDouble
* .LSOverride
* .DocumentRevisions-*
* .fseventsd
* .Spotlight-V*
* .TemporaryItems
* .Trashes
* .VolumeIcon.icns
* .com.apple.timemachine.donotpresent
* .AppleDB
* .AppleDesktop
* .apdisk
and conditionally ._foo.jpg if foo.jpg is also being uploaded