Re: [PATCH 19/20] abbrev: support relative abbrev values

> On Wed, Jun 13 2018, Junio C Hamano wrote:
>
>> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>>
>>> E.g. here's a breakdown of my dotfiles repo:
>>>
>>>     $ git -c core.abbrev=4 log  --pretty=format:%h|perl -nE 'chomp;say length'|sort|uniq -c|sort -nr
>>>         784 4
>>>          59 5
>>>           7 6
>>>
>>> I don't have a single commit that needs 7 characters, yet that's our
>>> default. This is a sane trade-off for the kernel, but for something
>>> that's just a toy or something you're playing around with something
>>> shorter can make sense.
>>>
>>> SHA-1s aren't just written down, but also e.g. remembered in wetware
>>> short-term memory.
>>
>> That's a fine example of what I called "supporting absurdly small
>> absolute values like 4"; I still do not see why you want "negative
>> relative values" from that example.
>
> Because hardcoding -2 is very different than setting it to 5, because
> the -2 will scale to the size of the repository, but 5 is just 7-2 where
> 7 is our default value.
>
> So, in general if you want less future proof hashes by some
> probabilistic metric (whether you use core.validateAbbrev or not) you'd
> use -2 or -3, just like you might use +2 or +3 if you'd like to have
> more future-proof hashes (especially with core.validateAbbrev=true).