From: "Remo Senekowitsch" <remo@buenzli•dev>
To: "Junio C Hamano" <gitster@pobox•com>
Cc: "D. Ben Knoble" <ben.knoble@gmail•com>,
"Nico Williams" <nico@cryptonector•com>,
"Theodore Ts'o" <tytso@mit•edu>,
"Martin von Zweigbergk" <martinvonz@google•com>,
"Git Mailing List" <git@vger•kernel.org>,
"Edwin Kempin" <ekempin@google•com>,
"Scott Chacon" <scott@gitbutler•com>,
"philipmetzger@bluewin•ch" <philipmetzger@bluewin•ch>
Subject: Re: Semantics of change IDs (Re: Gerrit, GitButler, and Jujutsu projects collaborating on change-id commit footer)
Date: Wed, 23 Apr 2025 01:21:12 +0200 [thread overview]
Message-ID: <D9DJXDL6JJJ0.3BM1YMOSV5P0F@buenzli.dev> (raw)
In-Reply-To: <xmqq8qnr3jji.fsf@gitster.g>
On Wed Apr 23, 2025 at 12:42 AM CEST, Junio C Hamano wrote:
> "Remo Senekowitsch" <remo@buenzli•dev> writes:
>
>> Btw. since the thread was started, the implementation in Jujutsu has
>> been completed and I've been pushing commits with the change-id header
>> to various remotes for a while now. It works well. Forges can start
>> taking advantage of it. (I hope I find time to help work on that.)
>
> It should work well, until somebody finds your random is not random
> enough, right? Unlike our object name that depends on the contents
> (hence a duplicate unless the cryptographic hash function collides
> means they are truly the same commit), there is no grabally unique
> ID assigner involved in your implementation, right? Until
> sufficiently large number of people start using and large number of
> changes gets assigned IDs, it won't become an issue, but then how
> would it be different from what was raised in the earlier discussion
> to use the commit object name itself as the change ID for a commit
> that is not derived from anybody else, and copy that ID to commits
> that are derived from the original commit as the change ID shared
> among them? At least that would give us a much better uniqueness
> guarantee, wouldn't it? If you want to be able to tell between
> commit object name and change ID, I wouldn't object if you encode
> them using whatever mechanism.
Random number generators are well suited for this purpose, the only
requirement is that the distribution of generated numbers does not
massively deviate from a uniform probability distribution.
Commit hashes have 160 bits of information, the change-ids used by
Jujutsu today have 128 bits. That's still plenty to make random
collisions practically irrelevant.
And anyway, the situation of colliding change-ids will be somewhat of
a normal event due to cherry-picking etc. Jujutsu can deal with this
situation just fine today. Colliding change-ids are simply not as much
of a problem as colliding commit hashes.
next prev parent reply other threads:[~2025-04-22 23:21 UTC|newest]
Thread overview: 118+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-02 18:48 Gerrit, GitButler, and Jujutsu projects collaborating on change-id commit footer Martin von Zweigbergk
2025-04-02 19:34 ` Remo Senekowitsch
2025-04-02 19:49 ` Konstantin Ryabitsev
2025-04-02 19:45 ` Konstantin Ryabitsev
2025-04-02 19:52 ` Martin von Zweigbergk
2025-04-03 9:09 ` Patrick Steinhardt
2025-04-03 10:38 ` Remo Senekowitsch
2025-04-03 11:06 ` Patrick Steinhardt
2025-04-03 15:56 ` Elijah Newren
2025-04-03 16:25 ` Remo Senekowitsch
2025-04-03 16:38 ` Elijah Newren
2025-04-03 21:46 ` Martin von Zweigbergk
2025-04-04 9:41 ` Patrick Steinhardt
2025-04-03 15:39 ` Elijah Newren
2025-04-03 16:40 ` Remo Senekowitsch
2025-04-03 22:11 ` Kane York
2025-04-04 2:28 ` Elijah Newren
2025-04-04 2:40 ` Elijah Newren
2025-04-04 3:47 ` Martin von Zweigbergk
2025-04-04 4:03 ` Nico Williams
2025-04-04 4:59 ` Elijah Newren
2025-04-04 5:21 ` Martin von Zweigbergk
2025-04-04 9:29 ` Patrick Steinhardt
2025-04-03 17:48 ` Theodore Ts'o
2025-04-03 20:31 ` Remo Senekowitsch
2025-04-05 2:09 ` Theodore Ts'o
2025-04-03 18:10 ` Nico Williams
2025-04-03 21:45 ` Remo Senekowitsch
[not found] ` <Z+8GoNrdaJlmNpGm@ubby>
2025-04-04 0:05 ` Remo Senekowitsch
2025-04-04 3:52 ` Nico Williams
2025-04-04 7:41 ` Remo Senekowitsch
2025-04-04 16:08 ` Nico Williams
2025-04-03 22:05 ` Martin von Zweigbergk
2025-04-03 22:13 ` Nico Williams
2025-04-03 22:47 ` Martin von Zweigbergk
2025-04-04 2:06 ` Elijah Newren
2025-04-04 3:11 ` Nico Williams
2025-04-04 4:08 ` Martin von Zweigbergk
2025-04-04 4:23 ` Nico Williams
2025-04-04 9:34 ` Patrick Steinhardt
2025-04-04 16:04 ` Nico Williams
2025-04-07 8:00 ` Patrick Steinhardt
2025-04-07 20:59 ` Junio C Hamano
2025-04-07 21:36 ` Nico Williams
2025-04-08 12:55 ` Theodore Ts'o
2025-04-08 15:53 ` Nico Williams
2025-04-09 12:19 ` Theodore Ts'o
2025-04-09 12:56 ` Junio C Hamano
2025-04-09 19:13 ` Nico Williams
2025-04-10 8:29 ` Junio C Hamano
2025-04-10 21:40 ` Martin von Zweigbergk
2025-04-09 16:54 ` Semantics of change IDs (Re: Gerrit, GitButler, and Jujutsu projects collaborating on change-id commit footer) Nico Williams
2025-04-09 18:02 ` Junio C Hamano
2025-04-09 18:35 ` Nico Williams
2025-04-09 19:14 ` Eric Sunshine
2025-04-09 19:31 ` Nico Williams
2025-04-10 13:44 ` Theodore Ts'o
2025-04-10 16:18 ` Junio C Hamano
2025-04-11 15:48 ` Theodore Ts'o
2025-04-11 16:38 ` Konstantin Ryabitsev
2025-04-11 17:44 ` Junio C Hamano
2025-04-12 23:13 ` Theodore Ts'o
2025-04-14 15:13 ` Junio C Hamano
2025-04-15 22:30 ` Remo Senekowitsch
2025-04-16 0:09 ` Junio C Hamano
2025-04-16 0:21 ` Jacob Keller
2025-04-15 21:38 ` Jacob Keller
2025-04-14 19:54 ` D. Ben Knoble
2025-04-14 21:34 ` Nico Williams
2025-04-15 21:44 ` Jacob Keller
2025-04-16 11:36 ` Remo Senekowitsch
2025-04-22 20:17 ` D. Ben Knoble
2025-04-22 22:24 ` Remo Senekowitsch
2025-04-22 22:42 ` Junio C Hamano
2025-04-22 22:51 ` Nico Williams
2025-04-22 23:47 ` Remo Senekowitsch
2025-04-23 0:32 ` Nico Williams
2025-04-23 1:15 ` Remo Senekowitsch
2025-04-23 4:45 ` Nico Williams
2025-04-22 23:49 ` Junio C Hamano
2025-04-23 1:02 ` Nico Williams
2025-04-23 4:47 ` Nico Williams
2025-04-22 23:21 ` Remo Senekowitsch [this message]
2025-04-23 5:07 ` Martin von Zweigbergk
2025-04-23 15:51 ` Junio C Hamano
2025-04-23 16:19 ` Martin von Zweigbergk
2025-06-06 13:04 ` Toon Claes
[not found] ` <aAgWytQNqtLzg2TU@ubby>
2025-04-23 0:25 ` Remo Senekowitsch
2025-04-23 0:45 ` Nico Williams
2025-04-23 12:58 ` How GitLab does/doesn't need change IDs (was Re: Semantics of change IDs) Toon Claes
2025-04-23 18:59 ` Nico Williams
2025-05-10 19:32 ` Semantics of change IDs (Re: Gerrit, GitButler, and Jujutsu projects collaborating on change-id commit footer) D. Ben Knoble
2025-05-10 19:46 ` D. Ben Knoble
2025-05-10 20:31 ` Martin von Zweigbergk
2025-05-12 17:03 ` Junio C Hamano
2025-05-12 17:19 ` Martin von Zweigbergk
2025-05-14 14:38 ` Junio C Hamano
2025-05-15 10:31 ` Oswald Buddenhagen
2025-05-15 16:32 ` Jacob Keller
2025-05-15 19:59 ` Junio C Hamano
2025-05-15 20:10 ` Nico Williams
[not found] ` <aCJi+4q6DZhnfdy+@ubby>
2025-05-12 21:43 ` Martin von Zweigbergk
2025-05-12 22:04 ` brian m. carlson
2025-06-06 12:28 ` Toon Claes
2025-06-06 15:44 ` Junio C Hamano
2025-05-13 21:22 ` D. Ben Knoble
2025-04-07 22:51 ` Gerrit, GitButler, and Jujutsu projects collaborating on change-id commit footer Remo Senekowitsch
2025-04-08 0:10 ` Junio C Hamano
2025-04-08 5:35 ` Martin von Zweigbergk
2025-04-08 14:27 ` Junio C Hamano
2025-04-08 15:58 ` Phillip Wood
2025-04-08 16:27 ` Nico Williams
2025-04-12 21:32 ` Junio C Hamano
2025-04-16 0:24 ` Jacob Keller
2025-05-14 15:08 ` Kristoffer Haugsbakk
2025-04-08 14:27 ` Junio C Hamano
2025-08-19 14:04 ` Askar Safin
2025-08-19 16:44 ` Ben Knoble
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