Re: [PATCH 8/9] for-each-ref: add option to fully dereference tags

From: Patrick Steinhardt <ps@pks.im>
Date: Nov 8, 2023, 07:19 UTC
Message-ID: <ZUs2kxOEr4vqCJi0@tanuki>
In-Reply-To: <xmqq4jhx7x8l.fsf@gitster.g>

On Wed, Nov 08, 2023 at 12:14:02PM +0900, Junio C Hamano wrote:

Show 12 quoted lines

> Victoria Dye <vdye@github.com> writes:
> 
> > I think `^{}fieldname` would be a good candidate, but it's *extremely*
> 
> Gaah.  Why?  fieldname^{} I may understand, but in the prefix form?
> 
> In any case, has anybody considered that we may be better off to
> declare that "*field" peeling a tag only once is a longstanding bug?
> 
> IOW, can we not add "fully peel" command line option or a new syntax
> and instead just "fix" the bug to fully peel when "*field" is asked
> for?

I see where you're coming from, but I wonder whether this wouldn't break scripts. To me, the documentation seems to explicitly state that this will only deref tags once:

    If fieldname is prefixed with an asterisk (*) and the ref points at
    a tag object, use the value for the field in the object which the
    tag object refers to (instead of the field in the tag object).

So changing that now would break both the documented and the actual behaviour. Now whether anybody actually cares about such a breaking change is of course a different question, and you're probably correct that in practice nobody does.

Patrick

Show 27 quoted lines

> An application that cares about handling a chain of annotatetd tags
> would want to be able to say "this is the outermost tag's
> information; one level down, the tag was signed by this person;
> another level down, the tag was signed by this person, etc."  which
> would mean either
> 
>  * we have a syntax that shows the information from all levels
>    (e.g., "**taggername" may say "Victoria\nPatrick\nGitster")
> 
>  * we have a syntax that allows to specify how many levels to peel,
>    (e.g., "*0*taggername" may be the same as "taggername",
>    "*1*taggername" may be the same as "*taggername") plus some
>    programming construct like variables and loops.
> 
> but the repertoire being proposed that consists only of "peel only
> once" and "peel all levels" is way too insufficient.
> 
> Note that I do not advocate for allowing inspection of each levels
> separately.  Quite the contrary.  I would say that --format=<>
> placeholder should not be a programming language to satisify such a
> niche need.  And my conclusion from that stance is "peel once" plus
> "peel all" are already one level too many, and "peel once" was a
> very flawed implementation from day one, when 9f613ddd (Add
> git-for-each-ref: helper for language bindings, 2006-09-15)
> introduced it.
> 
>