Re: [PATCH v4 00/18] Extending the shelf-life of "git describe" output

> Jeff King <peff@peff.net> writes:
> 
> > However, if you feed a partial sha1 for which there are
> > multiple matches, none of which satisfy the disambiguation hint, then we
> > used to say "short SHA1 is ambiguous", and now we don't.
> 
> In finish_object_disambiguation(), if the candidate hasn't been
> checked, there are two cases:
> 
>  - It is the first and only object that match the prefix; or
>  - It replaced another object that matched the prefix but that
>    object did not satisfy ds->fn() callback.
> 
> And the former case we set ds->candidate_ok to true without doing
> anything else, while for the latter we check the candidate, which
> may set ds->candidate_ok to false.

> At this point in the code, ds->candidate_ok can be false only if
> this last-round check found that the candidate does not pass the
> check, because the state after update_candidates() returns cannot
> satisfy
> 
>     !ds->ambiguous && ds->candidate_exists && ds->candidate_checked
> 
> and !ds->canidate_ok at the same time.
> 
> Hence, when we execute this "return", we know we have seen more than
> one object that match the prefix (and none of them satisfied ds->fn),
> meaning that we should say "the short name is ambiguous", not "there
> is no object that matches the prefix".