[dnanian]

We've done quite a bit of initial investigation into this, and the file size increase is, indeed, due to compressed files expanding during the copy.

This is not necessarily the same thing as the 'recopying', although the two issues are combined in this thread.

Spot checks of Finder, cp, tar and others shows that they're also expanding the files on copy. Since we use the base-level copy calls that Apple provides, and supplement that with additional metadata copies/checks, and the "external" size looks the same, we both assumed the base call was handling this properly and didn't catch it when looking at the file sizes themselves (since they're reported at their uncompressed size).

We're investigating how to avoid this expansion, and continuing to determine why things are being copied that you'd think wouldn't; more as I've got it (although I might move to blogging about this so it's more useful to others and other developers running into the same problem).