Re: [PATCH v5] rev-list: teach --no-object-names to enable piping

[Jeff King <peff@peff.net>]

On Wed, Jun 19, 2019 at 01:56:56PM -0700, Emily Shaffer wrote:

> Allow easier parsing by cat-file by giving rev-list an option to print
> only the OID of a non-commit object without any additional information.
> This is a short-term shim; later on, rev-list should be taught how to
> print the types of objects it finds in a format similar to cat-file's.
> [...]

I missed some of the intermediate rounds, but fortunately Junio already
said everything I was going to. :) This version looks good to me, though
with one minor nit:

> diff --git a/Documentation/git-rev-list.txt b/Documentation/git-rev-list.txt
> index 88609ff435..9392760b25 100644
> --- a/Documentation/git-rev-list.txt
> +++ b/Documentation/git-rev-list.txt
> @@ -48,6 +48,7 @@ SYNOPSIS
>  	     [ --date=<format>]
>  	     [ [ --objects | --objects-edge | --objects-edge-aggressive ]
>  	       [ --unpacked ]
> +	       [ --object-names | --no-object-names ]
>  	       [ --filter=<filter-spec> [ --filter-print-omitted ] ] ]
>  	     [ --missing=<missing-action> ]
>  	     [ --pretty | --header ]

Here you put --object-names along with the --objects. Which kind of
makes sense, but everything else in that block is about choosing _which_
commits to show. In the short help, you put it near --pretty:

> @@ -49,6 +49,7 @@ static const char rev_list_usage[] =
>  "    --objects | --objects-edge\n"
>  "    --unpacked\n"
>  "    --header | --pretty\n"
> +"    --[no-]object-names\n"
>  "    --abbrev=<n> | --no-abbrev\n"
>  "    --abbrev-commit\n"
>  "    --left-right\n"

which I think makes more sense. I think maybe you were trying to imply
that "--object-names" is not useful unless you're also using
"--objects". Which is true, but I'm not sure it's obvious from that mass
of brackets (and I think is sufficiently covered in the actual option
descriptions you give later).

> +test_expect_success '--no-object-names and --object-names are last-one-wins' '
> +	git rev-list --objects --no-object-names --object-names --all >output &&
> +	grep wanted_file output &&
> +	git rev-list --objects --object-names --no-object-names --all >output &&
> +	! grep wanted_file output
> +'

We don't generally test this behavior for each option, since it would
lead to a ton of uninteresting tests (and parse-options generally just
handles it).  But after our discussion about --no-abbrev, I can see how
you might be more interested in the topic. :) So I'm OK with it either
way.

-Peff