My guess is no, but this is not a definitive answer.
I first created a very large (~160 MB) .txt file, and made changes to the file in TextEdit. As expected, that file and its versions showed up in /.DocumentRevisions-V100/PerUID. The files appeared to be ~160 MB to ls, but according to du -h they used 0B on disk. The hard link count for each file was 1. A folder called .cs (chunk storage) under /.DocumentRevisions-V100 had grown by about 110 MB.
Every time I changed the file, the following happened in /.DocumentRevisions-V100:
- A ~160 MB file was created in
/.DocumentRevisions-V100/staging/. The hard link count for this file is 1.
- That file appeared to move to
/.DocumentRevisions-V100/PerUID/<UID>/<#>/com.apple.documentVersions. The hard link count remained 1.
- That ~160 MB file became 0B, and the size of
/.DocumentRevisions-V100/.cs grew by about 2 MB.
The free space of the drive (df) was consistent with what du told me. Free space would go down significantly, and then return to nearly what it was before saving a new version.
Next, I tried to shred the file with Secure Empty Trash. OS X seems to use a program called Locum to securely delete the file. Attaching fs_usage to Locum shows an awful lot of reads and writes to the original .txt file. While Locum is doing its thing, all the versions under /.DocumentRevisions-V100/PerUID can still be accessed with data intact. After Locum is done writing over the data, it unlinks the original .txt file, and the versions in /.DocumentRevisions-V100/PerUID suddenly disappear. Locum then moves on to anything else in the Trash, while never touching /.DocumentRevisions-V100.
Whatever is in /.DocumentRevisions-V100 is not being securely erased.
EDIT: I should add that whatever is in /.DocumentRevisions-V100 is somehow obfuscated or compressed (the folder was only ~120 MB). I haven’t yet read the versions or filesystem sections of Siracusa’s review… maybe there are clues in there.
My take on this is that Apple does not want users to see iCloud as another Dropbox or (even worse) another iDisk. Although I am not certain of what I about to write, my theory on iCloud based on what I have read so far is that there will not be an iDisk-like drive or a Dropbox-like special folder. Instead, iCloud's approach will be app-centric in that you will open the app you want and then get your files from iCloud regardless of which iPad, iPhone or Mac you're using at the time. In the practical sense, that most likely means that iCloud will "magically" get you the latest file as you switch contexts, but not the file's Versions history--that will be for now a Lion-only feature.
I do not anticipate Dropbox integrating with Versions or iCloud any time soon because it is not in the best interest of Dropbox for you to use iCloud and vice-versa. Especially considering how both have a vested interested in earning your storage needs business (And this is even more true for Dropbox than it is for Apple). At the technical level, there is no reason why they wouldn't be able to coexist: Lion would see the Dropbox folder as any other folder and allow you to keep its Versions history. Dropbox, in turn, will see the hidden folders used by Versions as folders it needs to sync up--unless Dropbox does not currently support syncing hidden folders. I have not tested to see what Dropbox does with them
It is important to remember that Dropbox's very own version history is kept at their server. That means that there would not be a physical conflict between the historic files Dropbox keeps track of and what Lion keeps track on that same folder for Versions. It will be up to you to choose where to go and look: On Lion's friendly Versions UI or on Dropbox's web-based file history. Of course, the caveat is that the individual historic entries won't be exactly the same. I guess you can say there will be two "versions" of the same story (pun intended).
I do not think there is a need for a workaround as there really is no technical conflict. iCloud and Dropbox will both do their thing and I will probably end up using Versions in Lion to browse the file history of all of my files, even those in the Dropbox folder, because it is friendlier to use. If I cannot use Versions on a particular file because its app doesn't yet support it, and if this is a file that I have in Dropbox, then I will go and take a look at the Dropbox website to get its version history. Hope this helps.
Best Answer
If you want to delete old versions from a document directly: