on when to checksum

Linus, 

I think you have made a mistake by moving the sha1 checksum from the zipped form to the inflated form. Here is why:

What you have set in motion with `git' is an ad-hoc p2p network for sharing filesystem trees -- a global distributed filesystem. I believe your starter here has a good chance of taking off to be much, much larger than just a tool for the kernel.

A subset of your work: blobs and blob databaes, has much wider application than just sharing trees: Those parts of `git' can form a very solid foundation for many other applications as well. To the extent `git' succeeds in the context of the kernel, it will be invested in and extended and generalized --- and the kernel project will benefit. So don't ignore those wider applications even though they are not your focus today: they will generate investment that feeds back to your project.

Your `git' is silent on transports and mirroring of blob databases -- tasks for scripting, sure -- but those elements won't be far behind.

Eventually, slinging around blobs as atomic elements of payloads will become very common.

The blob handle (aka "address")/payload model of a blob db is very clean and simple. In a network of nodes speaking to one and other by exchanging blobs, I forsee a prominent need for intermediate nodes that process blobs "blindly" and as quickly as possible.

Blob compression is mostly goofy if regarded just as a way to save on (diminishingly cheap) disk space but it is mostly sane if regarded as a way to cut the cost of network bandwidth roughly in half.

Must intermediate nodes inflate the payloads passing through them or which they cache just to validate them? That's not a desirable otucome for many obvious reasonhs.

There *are* concerns about checksumming zips: it is necessary to nail down the zip process and make sure it is absolutely and permanently deterministic for this application. But *that* is the problem to solve, not avoid by moving what the checksum refers to.

Thanks, -t