Re: [PATCH 0/2] Documentation updates for SHA-256

From: Derrick Stolee <stolee@gmail.com>
Date: Aug 14, 2020, 02:33 UTC
Message-ID: <da077fb0-14bb-b84f-c526-d759ebc9f5eb@gmail.com>
In-Reply-To: <20200813224901.2652387-1-sandals@crustytoothpaste.net>

On 8/13/2020 6:48 PM, brian m. carlson wrote:

> As was pointed out recently, some of our documentation doesn't properly
> reflect the new support for SHA-256.

Just to bring up some subtlety in Martin's message [1], there is some valid concern that the existing file formats are not correctly versioned "in a vacuum." When they are in a repository that has SHA-256 set as its hash algorithm, Git interprets these file formats correctly, but if a *.pack file (and its *.idx) happened to be copied into the pack directory of a Git repository still in SHA-1 mode, then Git would get confused and probably fail miserably.

Is that really a concern? Maybe, but also Git will never move data like that. The main thing is to focus on compatibility of the .git directory as a whole (and the protocol, as we move into inter-operability mode).

[1] https://lore.kernel.org/git/CAN0heSptiJL9d86ZeNPMUaZeTA68juwTyf3K-uWR=K-vt=1Hrg@mail.gmail.com/

>  This series updates the pack and
> index documentation to reflect that these formats can handle SHA-256,
> and updates the transition plan to reflect what we've implemented and
> what the next steps are.

These patches are good to help clarify these formats in the new world.

Thanks, -Stolee