Re: [PATCH v2 1/8] for-each-ref: add --stdin option

[Jeff King <peff@peff.net>]

On Wed, Mar 15, 2023 at 12:24:18PM -0700, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > ... we may
> > want some kind of "literal" mode, that takes in a list of refs rather
> > than a list of patterns, and does a sorted-merge with the list of
> > available refs (or uses a hash table, I guess, but for-each-ref also
> > tries to avoid even being linear in the total number of refs, so you'd
> > still want to find the lowest/highest to bound the iteration).
> 
> Exactly.
> 
> I actually was wondering if "literal" mode can just take a list of
> <things>, and when a <thing> is not a refname, use it as if it
> were. I.e. %(refname) would parrot it, while %(refname:short) would
> not shorten and still parrot it, if the <thing> is 73876f4861c, but
> something like %(subject) would still work.

Yeah, I think that would nicely solve the quadratic issue _and_ the
"we are stuck using only ref tips" issue. I like it.

> For that, I suspect ref-filter.c::filter_refs() would need to learn
> a different kind fo finter->kind that iterates over the literal
> "refs" that was fed from the standard input, instead of calling
> for_each_fullref_in() for the given hierarchy, but the new iterator
> should be able to reuse the ref_filter_hander() for the heavy
> lifting.

Yeah, that sounds about right from my recollection of the code. I
suspect there may be other sharp edges (e.g., asking for %(upstream)
isn't meaningful for a non-ref). But softening those is actually
something I think we want to do in the long run, as it helps with the
long-term goal of sharing pretty-printing code between ref-filter,
cat-file, and pretty.c.

-Peff