The question of keeping a FSFS mirror repository using rsync came up. For FSFS f4 it's possible to do an rsync of just the rev file + revprop file + 'current' from post-commit. (Yes, the prior revisions must be a byte-for-byte match, and min-unpacked-rev must agree as well. As to rep-cache.db, it is not needed on the mirror.)
In short, for f4 it seems to be a pretty efficient way of sync, although of course it comes without forward-compatibility guarantees (i.e., it has the acceptable-to-our-use-case caveat that it might stop working come 1.8 or 1.9). Does this property hold for f6 / 1.8?
