On Fri, 29 Apr 2005, Tom Lord wrote:

	1) the ancestry of their modified tree

	2) the complete contents of their modified tree

	3) input data for a patching program (let's call it "PATCH")
	   which, at the very least, satisfies the equation:

		MOD_TREE = PATCH (this_diff, ORIG_TREE)

On the other hand, signing documents which represent a {(1),(3)} pair
with robust accuracy is, in most cases, much much less expensive than
signing {(1),(2)} pairs with robust accuracy. 

Not so.

It may be less expensive in your world, but that's the whole point of git: 
it's _not_ less expensive in the git world. 

In the git world, 1 and 2 aren't even separate things. They go together. 
And you just sign it. End of story. It's so cheap to sign that it's not 
even funny.

More importantly, signing 3 is meaningless. 3 only makes sense with a 
known starting point. You should never sign a patch without also saying 
what you're patching. 

And once you do that, 1+2 and 1+3 are _exactly_ the same thing.

And since git always works on the 1+2 level, it would be inexcusably
stupid to sign anything but that. 3 doesn't even exist per se, although 
it's obviously fully defined by 1+2.

So I don't see your point. You complain about git signing, but you 
complain on grounds that do not _exist_ in git, and then your alternative 
(1+3) which is senseless in a git world doesn't actually end up being 
anything really different - just more expensive.

		Linus