Re: add 'ls-remote' option to limit output records

[Jeff King <peff@peff.net>]

On Fri, Apr 26, 2019 at 12:32:51PM -0700, Bryan Turner wrote:

> >         $ git ls-remote -n1 --tags --sort=v:refname origin "v*"
> [...]
> With the v2 wire protocol, the client could provide a prefix (like
> `refs/tags/`, or potentially `refs/tags/v`) to reduce what the server
> included in the ref advertisement, but even the v2 protocol doesn't
> have anything for telling the server "Version parse these names and
> then return the first N". That means the parsing, sorting and trimming
> for the advertised tags would still all have to happen locally. (I'm
> sure someone can correct me if I've misstated what protocol v2 can do
> for filtering, but I don't see any "ls-refs" options that look like
> they enable anything other than prefix matching.)

No, that sounds right. The "--tags" in the original command should cause
v2 to ask only for refs/tags/. But because of the way ls-remote matching
works, "v*" is not a pure prefix match, and would find
"refs/tags/foo/v1.2.3". So we can't use protocol-level matching to ask
for "refs/tags/v*".

There are no provisions in the protocol for sorting, nor for limiting
the output.

I didn't check, but I suspect some hosting-platform APIs might be able
to answer this with a single query.

-Peff