Re: [PATCH 2/2] pretty: add merge and exclude options to %(describe)

From: Jeff King <peff@peff.net>
Date: Feb 17, 2021, 18:31 UTC
Message-ID: <YC1hHYeCmC6+heWZ@coredump.intra.peff.net>
In-Reply-To: <b7bd37c4-ab13-0297-da46-716e26de10d6@web.de>

On Sun, Feb 14, 2021 at 11:10:57AM +0100, René Scharfe. wrote:

Show 6 quoted lines

> Allow restricting the tags used by the placeholder %(describe) with the
> options match and exclude.  E.g. the following command describes the
> current commit using official version tags, without those for release
> candidates:
> 
>    $ git log -1 --format='%(describe:match=v[0-9]*,exclude=*rc*)'

An interesting side effect of this series is that it allows remote users asking for archives to fill in this data, too (by using export-subst placeholders). That includes servers allowing "git archive --remote", but also services like GitHub that will run git-archive on behalf of clients.

I wonder what avenues for mischief this provides. Certainly using extra CPU to run git-describe. But I guess also probing at otherwise hidden refs using the match/exclude system (though since it's limited to refs/tags/, that's pretty unlikely).

I present this mostly as an observation, not an objection. Certainly we already have %D which can look at hidden refs. And I strongly suspect that the server-side git-upload-archive does not respect hidden refs when resolving object names in the first place.

Kind of an interesting thought as we extend the formatting language, though. I generally think of them as something that is always under control of caller, but export-subst's $Format$ will come from the repo contents.

-Peff