Re: --abbrev-commit gives longer hash than necessary

From: Bryan Turner <bturner@atlassian.com>
Date: Jun 30, 2016, 20:14 UTC
Message-ID: <CAGyf7-E0VbkCC29y=OuNHL5_KA=qoXEsrChxvXcGmfZ_CjTzqQ@mail.gmail.com>
In-Reply-To: <20160630193845.TbelqPPHx%steffen@sdaoden.eu>

Steffen,

Git commands generally have a 7 character minimum by default when abbreviating hashes, even if fewer characters are still (currently) unique. Per the documentation:

   core.abbrev
       Set the length object names are abbreviated to. If unspecified,
       many commands abbreviate to 7 hexdigits, which may not be enough
       for abbreviated object names to stay unique for sufficiently long
       time.

You may be able to set core.abbrev to a smaller value to get even shorter hashes, but the shorter you go the more likely you are to find once-unique hashes no longer are, as your repository grows over time. The default isn't just about what's likely to be unique now; it's about what's likely to stay unique for a period of time.

Hope this helps! Bryan Turner

On Thu, Jun 30, 2016 at 12:38 PM, Steffen Nurpmeso <steffen@sdaoden.eu> wrote:

Show 38 quoted lines

> Hello, for your possible interest.
>
> For some time (currently with 2.9.0) know see that a single commit
> gives a longer hash than necessary, even though there is no
> ambiguity:
>
>   ?0[steffen@wales ]$ git longca|
>   awk 'BEGIN{l7=0;l8=0}\
>     /^[[:alnum:]]{7} /{++l7;next}\
>     /^[[:alnum:]]{8} /{++l8;print}\
>   END{print "L7 " l7 " L8 " l8}'
>   786d0c9c [mimepipe.2] send.c:sendpart(): force iconv(3)+ for TEXT part handlers..
>   L7 3364 L8 1
>
> So it is only this single commit.. but why?
>
>   ?0[steffen@wales ]$ git long1 786d0c9
>   786d0c9c [mimepipe.2] send.c:sendpart(): force iconv(3)+ for TEXT part handlers..
>   ?0[steffen@wales ]$ git long1 786d0c
>   786d0c9c [mimepipe.2] send.c:sendpart(): force iconv(3)+ for TEXT part handlers..
>   ?0[steffen@wales ]$ git long1 786d0
>   786d0c9c [mimepipe.2] send.c:sendpart(): force iconv(3)+ for TEXT part handlers..
>   ?0[steffen@wales ]$ git long1 786d
>   786d0c9c [mimepipe.2] send.c:sendpart(): force iconv(3)+ for TEXT part handlers..
>
> Not really ambiguous:
>
>   ?0[steffen@wales ]$ git long|cut -f1 -d' '|grep ^786
>   786d0c9c
>   786f219
>
> Ciao!
>
> --steffen
> --
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