Re: [PATCH 0/4] rev-list: introduce NUL-delimited output mode

On Mon, Mar 10, 2025 at 02:28:25PM -0500, Justin Tobler wrote:

To make machine parsing easier, this series introduces a NUL-delimited
output mode for git-rev-list(1) via a `-z` option following a suggestion
from Junio in a previous thread[1]. In this mode, instead of LF, each
object is delimited with two NUL bytes and any object metadata is
separated with a single NUL byte. Examples:

        <oid> NUL NUL
        <oid> [NUL <path>] NUL NUL
        ?<oid> [NUL <token>=<value>]... NUL NUL

In this mode, path and value info are printed as-is without any special
encoding or truncation.

I think this is a good direction, but I have two compatibility
questions:

  1. What should "git rev-list -z --stdin" do? In most other programs
     with a "-z" option it affects both input and output. I don't
     particularly care about this case myself, but it will be hard to
     change later. So we probably want to decide now.

  2. I was a little surprised that rev-list already takes a "-z" option,
     but it doesn't seem to do anything. I guess it's probably picked up
     via diff_opt_parse(), though (I think) you can't actually trigger a
     diff via rev-list itself. So even though this is a change in
     behavior, probably nobody would have been using it until now?

     If it is possible to see some effect from "-z" now (I didn't dig
     very far), then it may be better to continue to let the diff
     options parser handle it, and simply pick the result out of
     revs.diffopt.line_termination. As your patch 3 is written, I think
     the diff code probably doesn't see it anymore at all.

-Peff