Re: [PATCH] diff: fix up SHA-1 abbreviations outside of repository

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> I agree that it may be an accident waiting to happen, though, as soon as
> some buried sub-function needs to care about the distinction.

Yes to that.

>> I wonder if we're better off if we made sure that diff_no_index()
>> works the same way regardless of the value of "have_repository"
>> field?
>
> If you mean adding a diffopt flag like "just abbreviate everything to
> FALLBACK_DEFAULT_ABBREV even if we're in a repository", and then setting
> that in diff_no_index(), I agree that is a lot cleaner.

I am not sure if that is what I meant (I no longer sure what exactly
I meant to say there TBH), but this is probably not limited to the
default abbrev length aka core.abbrev configuration.  Don't we have
other configuration settings we may read from $HOME/.gitconfig (and
possibly per-repository .git/config, if we did discovery but were
explicitly given "--no-index") that want to affect the behaviour of
the command?  

I guess what I wanted, with "the same way", to see happen was that
"have_repository" should be only controling how and from what files
the configuration is read, and the behaviour of the command should
be controlled by the values read from the configuration after that.

Specifically, even if we were running with "--no-index", if we know
we have access to the current repository discovered by setting it up
gently, I do not think it is bad to ask find_unique_abbrev() to come
up with an appropriate abbreviation.  So the fact that patch in
question has to flip the have_repository bit off, if it is done in
order to affect what diff_abbrev_oid() does, smells quite fishy from
that point of view.