Re: git-fetch without a hash

[Simon Tournier]

Hi,

On dim., 05 févr. 2023 at 18:44, bokr@bokr.com wrote:

>> From my understanding, we could have something like,
>> 
>>       (sha256 (no-hash))
>> 
>> where ’no-hash’ would return a string, say
>> "0000000000000000000000000000000000000000000000000000" or whatever else
>> that would satisfy this hypothetical  ’sha256’ sanitizer.

> For portability to any hash algorithm that returns a hex string,
> how about letting them hash a zero-length string (which can never
> represent a package tarball or other archive), and using the
> resulting strings as no-hash flags?

Instead of “0000000000000000000000000000000000000000000000000000”, you
are proposing “0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73”
which is the Guix hash of empty.

> $ sha256sum /dev/null
> e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855  /dev/null

    $ touch foo
    $ guix hash foo
    0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73
    $ guix hash foo -f hex -H sha256
    e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

Yeah, probably better. :-)

> These strings must be unique for whatever hash algorithm,
> so a short table could be used to recognize them as
> no-hash indicators.

Well, I do not understand “These strings must be unique for whatever
hash algorithm”.  What do you mean?

Cheers,
simon