Re: State of NewHash work, future directions, and discussion
- Date: Mon, 11 Jun 2018 19:42:52 -0700
- From: Jonathan Nieder <jrnieder@xxxxxxxxx>
- Subject: Re: State of NewHash work, future directions, and discussion
brian m. carlson wrote:
> On Mon, Jun 11, 2018 at 12:01:03PM -0700, Jonathan Nieder wrote:
>> 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
Here, by 'always' I meant 'also'. Sorry for the confusion.
>> 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
> I'm happy to hear suggestions on how this should or shouldn't work. I'm
> seeing these things in my head, but it can be helpful to have feedback
> about what people expect out of the code before I spend a bunch of time
> writing it.
So far you're doing pretty well. :)
I just noticed that I have some copy-edits for the
hash-function-transition doc from last year that I hadn't sent out yet
(oops). I'll send them tonight or tomorrow morning.
>> brian m. carlson wrote:
>>> 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"?
> I mean situations like git update-index. We allow the user to insert
> any old invalid value (and in fact check that the user can do this).
> t0000 does this, for example.
I think we can forbid this in the new mode (using a test prereq to
ensure the relevant tests don't get run). Likewise for the similar
functionality in "git mktree" and "git hash-object -w".
>> 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.
> I have a hash that I've been using, but redoing the work would be less
> enjoyable. I'd rather write the tests only once if I can help it.
Thanks for the test fixes so far that make most of the test suite
For t0000, yeah, there's no way around having to hard-code the new