In addition to `.Spotlight-V100` and `.Trashes`, the following dotfiles
may appear at the root of all OSX volumes (not just external disks):
- `.DocumentRevisions-V100`: auto-save and versions storage
- `.fseventsd`: file system event storage
- `.Temporaryitems`: temp directory used by some applications instead of
/tmp and /var/tmp
- `.VolumeIcon.icns`: storage of custom icon for volume, if set
The .gitignore rule "Icon?" will also match directories such as
"icons/", at least on a case-insensitive file-system (this happened to
me on OS X 10.7). I only noticed this several days later because a
developer was complaining about missing icons in his repository. I don't
really know what type of files this rule is supposed to match, but I
guess the described behavior is not expected.