Database consistency after a successful pull

Subject Was: [PATCH] pull: gracefu[PAlly recover from delta retrieval failure.]

[snip lots of really good information about the thinking
 behind the design of the pull mechanisms ]

Ok, so would I be correct in the following assumptions about the validity of a 'consistent' .git/objects database:

============================================================

Commits:
	* May have the tree they refer to in the database
	* Must have their parents in the database

Trees:
	* Must have the blobs they refer to in the database
	* Must have the trees they refer to in the database

Deltas:
	* Must have the referred to object in the database

Blobs:
	* No references to check

============================================================

In short, the database would contain:

	* The entire commit history
	* Selected commits would have the entire tree available

Correct, or totally mistaken? If mistaken, what are the consitency rules?

[Oh, and does PGP signing my messages bug anybody? If so, I can stop
 doing that on this list]