From: Jonathan Nieder <jrnieder@gmail.com> To: "brian m. carlson" <sandals@crustytoothpaste.net> Cc: git@vger.kernel.org, Duy Nguyen <pclouds@gmail.com> Subject: Re: State of NewHash work, future directions, and discussion Date: Mon, 11 Jun 2018 12:01:03 -0700 [thread overview] Message-ID: <20180611190103.GB20665@aiede.svl.corp.google.com> (raw) In-Reply-To: <20180609205628.GB38834@genre.crustytoothpaste.net> Hi, brian m. carlson wrote: > Since there's been a lot of questions recently about the state of the > NewHash work, I thought I'd send out a summary. Yay! [...] > I plan on introducing an array of hash algorithms into struct repository > (and wrapper macros) which stores, in order, the output hash, and if > used, the additional input hash. Interesting. In principle the four following are separate things: 1. Hash to be used for command output to the terminal 2. Hash used in pack files 3. Additional hashes (beyond (2)) that we can look up using the translation table 4. Additional hashes (beyond (1)) accepted in input from the command line and stdin In principle, (1) and (4) would be globals, and (2) and (3) would be tied to the repository. I think this is always what Duy was hinting at. All that said, as long as there is some notion of (1) and (4), I'm excited. :) Details of how they are laid out in memory are less important. [...] > The transition plan anticipates a stage 1 where accept only SHA-1 on > input and produce only SHA-1 on output, but store in NewHash. As I've > worked with our tests, I've realized such an implementation is not > entirely possible. We have various tools that expect to accept invalid > object IDs, and obviously there's no way to have those continue to work. Can you give an example? Do you mean commands like "git mktree"? [...] > If you're working on new features and you'd like to implement the best > possible compatibility with this work, here are some recommendations: This list is great. Thanks for it. [...] > == Discussion about an Actual NewHash > > Since I'll be writing new code, I'll be writing tests for this code. > However, writing tests for creating and initializing repositories > requires that I be able to test that objects are being serialized > correctly, and therefore requires that I actually know what the hash > algorithm is going to be. I also can't submit code for multi-hash packs > when we officially only support one hash algorithm. Thanks for restarting this discussion as well. You can always use something like e.g. "doubled SHA-1" as a proof of concept, but I agree that it's nice to be able to avoid some churn by using an actual hash function that we're likely to switch to. Sincerely, Jonathan
next prev parent reply other threads:[~2018-06-11 19:01 UTC|newest] Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-06-09 20:56 brian m. carlson 2018-06-09 21:26 ` Ævar Arnfjörð Bjarmason 2018-06-09 22:49 ` Hash algorithm analysis brian m. carlson 2018-06-11 19:29 ` Jonathan Nieder 2018-06-11 20:20 ` Linus Torvalds 2018-06-11 23:27 ` Ævar Arnfjörð Bjarmason 2018-06-12 0:11 ` David Lang 2018-06-12 0:45 ` Linus Torvalds 2018-06-11 22:35 ` brian m. carlson 2018-06-12 16:21 ` Gilles Van Assche 2018-06-13 23:58 ` brian m. carlson 2018-06-15 10:33 ` Gilles Van Assche 2018-07-20 21:52 ` brian m. carlson 2018-07-21 0:31 ` Jonathan Nieder 2018-07-21 19:52 ` Ævar Arnfjörð Bjarmason 2018-07-21 20:25 ` brian m. carlson 2018-07-21 22:38 ` Johannes Schindelin 2018-07-21 23:09 ` Linus Torvalds 2018-07-21 23:59 ` brian m. carlson 2018-07-22 9:34 ` Eric Deplagne 2018-07-22 14:21 ` brian m. carlson 2018-07-22 14:55 ` Eric Deplagne 2018-07-26 10:05 ` Johannes Schindelin 2018-07-22 15:23 ` Joan Daemen 2018-07-22 18:54 ` Adam Langley 2018-07-26 10:31 ` Johannes Schindelin 2018-07-23 12:40 ` demerphq 2018-07-23 12:48 ` Sitaram Chamarty 2018-07-23 12:55 ` demerphq 2018-07-23 18:23 ` Linus Torvalds 2018-07-23 17:57 ` Stefan Beller 2018-07-23 18:35 ` Jonathan Nieder 2018-07-24 19:01 ` Edward Thomson 2018-07-24 20:31 ` Linus Torvalds 2018-07-24 20:49 ` Jonathan Nieder 2018-07-24 21:13 ` Junio C Hamano 2018-07-24 22:10 ` brian m. carlson 2018-07-30 9:06 ` Johannes Schindelin 2018-07-30 20:01 ` Dan Shumow 2018-08-03 2:57 ` Jonathan Nieder 2018-09-18 15:18 ` Joan Daemen 2018-09-18 15:32 ` Jonathan Nieder 2018-09-18 16:50 ` Linus Torvalds 2018-07-25 8:30 ` [PATCH 0/2] document that NewHash is now SHA-256 Ævar Arnfjörð Bjarmason 2018-07-25 8:30 ` [PATCH 1/2] doc hash-function-transition: note the lack of a changelog Ævar Arnfjörð Bjarmason 2018-07-25 8:30 ` [PATCH 2/2] doc hash-function-transition: pick SHA-256 as NewHash Ævar Arnfjörð Bjarmason 2018-07-25 16:45 ` Junio C Hamano 2018-07-25 17:25 ` Jonathan Nieder 2018-07-25 21:32 ` Junio C Hamano 2018-07-26 13:41 ` [PATCH v2 " Ævar Arnfjörð Bjarmason 2018-08-03 7:20 ` Jonathan Nieder 2018-08-03 16:40 ` Junio C Hamano 2018-08-03 17:01 ` Linus Torvalds 2018-08-03 16:42 ` Linus Torvalds 2018-08-03 17:43 ` Ævar Arnfjörð Bjarmason 2018-08-04 8:52 ` Jonathan Nieder 2018-08-03 17:45 ` brian m. carlson 2018-07-25 22:56 ` [PATCH " brian m. carlson 2018-06-11 21:19 ` Hash algorithm analysis Ævar Arnfjörð Bjarmason 2018-06-21 8:20 ` Johannes Schindelin 2018-06-21 22:39 ` brian m. carlson 2018-06-11 18:09 ` State of NewHash work, future directions, and discussion Duy Nguyen 2018-06-12 1:28 ` brian m. carlson 2018-06-11 19:01 ` Jonathan Nieder [this message] 2018-06-12 2:28 ` brian m. carlson 2018-06-12 2:42 ` Jonathan Nieder
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