From: Justin Tobler <jltobler@gmail.com>
Date: Wed, 05 Feb 2025 17:17:32 GMT
Subject: Re: [PATCH v4 0/2] rev-list: print additional missing object information
Message-ID: <4peozlz56kmdhziyq6uhsvm4t7atmwtbl7divyuqqb4l64wgom@z3adjdx7v5x2>
In-Reply-To: <xmqq5xlor0la.fsf@gitster.g>

On 25/02/05 05:18AM, Junio C Hamano wrote:
> Justin Tobler <jltobler@gmail.com> writes:
> 
> > One concern I currently have with this quoting approach is that it is a
> > bit more challenging to machine parse compared to something like using a
> > null byte to delimit between missing info. One option is, in a followup
> > series, introduce a git-for-each-ref(1) style format syntax. Maybe
> > something like: `--missing=print-info:%(path)%00%(type)`. I'm curious if
> > anyone may have thoughts around this.
> 
> Would it be so bad if we said that in -z mode with --info option,
> each record is terminated with two NUL bytes, and elements on a list
> of var=value pairs have a single NUL in between, or something silly
> like that?  The point is to get away with just a fixed format,
> without any customization.

I agree that some sort of fixed format would be preferable as it's less
complex while also being simpler to implement. I originally considered
using NUL but realized a single NUL byte to delimit between entries
wouldn't be sufficient to determine where each record would end. Using
two NUL bytes next to each other to mark the end of a record would work
though.

Since even a normal rev-list record may have an object name entry in
addition to its OID when the `--objects` option is set, maybe we could
introduce a `-z` option that always terminates a record with two NUL
bytes?

The output for `git rev-list -z --objects --missing=print-info` could
look something like the following (no LF at EOL):

  6aa71444d3d41315509c3f2cfe2d45d86cea20d7<NUL><NUL>
  f009994f5d7fc97c1e87b4dc7ad69057a07e85c4<NUL>foo/bar<NUL><NUL>
  ?f10f78c60046b2be841c9e2403960663439296c3<NUL>path=foo/bar/baz<NUL>type=blob<NUL><NUL>
  ?ead43a34efd775b58d6b3e86db6bc71bbedd2c1c<NUL>path=foo/bar/baz 2<NUL>type=blob<NUL><NUL>

Having two NUL bytes to delimit between records might be a bit odd in
the common case for git-rev-list(1) without the `--objects` and
`--missing` options since we would only expect a list of OIDs. Having
consistent `-z` option output irrespective of other options might be
preferable though.

If this approach seems reasonable, I can do so in a followup series.

Thanks
-Justin