"brian m. carlson" <sandals@xxxxxxxxxxxxxxxxxxxx> writes: > On 2025-05-12 at 21:43:46, Martin von Zweigbergk wrote: >> Random bytes has worked well for jj. > > I would like to suggest that we use a deterministic approach. People > rely on Git commits being deterministic, including in my stash > import/export series[0]. In addition, it's important to avoid any > allegations of side channels or leaking information in commits, which > would be a concern in many environments and which a deterministic > approach would avoid[1]. > > I'd suggest a simple SHA-256 hash of the original commit data (for both > SHA-1 and SHA-256 commits, but one that would change to a new hash if we > added one) or an HMAC-SHA-256 with a fixed and documented key. I was thinking: you cannot guarantee determinism, because the change-ID would remain stable, even when if the underlaying data on which it was generated changes. But on second thought, _some_ determinisn *can* be useful, for example when different tools try to generate a change-ID for the same source commit. > I would also recommend a config option to avoid creating these IDs for > those who don't want them included for privacy reasons. I expect to set > such an option, for instance. Fair enough. -- Cheers, Toon
