Re: [PATCH 2/2] ls-files: introduce "--object-only" option

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

On Wed, Jun 15 2022, ZheNing Hu via GitGitGadget wrote:

> From: ZheNing Hu <adlternative@gmail.com>
>
> --object-only is an alias for --format=%(objectname),
> which output objectname of index entries, taking
> inspiration from the option with the same name in
> the `git ls-tree` command.
>
> --object-only cannot be used with --format, and -s, -o,
> -k, --resolve-undo, --deduplicate, --debug.
>
> Signed-off-by: ZheNing Hu <adlternative@gmail.com>
> ---
>  Documentation/git-ls-files.txt |  8 +++++++-
>  builtin/ls-files.c             | 36 +++++++++++++++++++++++++++++++++-
>  t/t3013-ls-files-format.sh     | 34 ++++++++++++++++++++++++++++++++
>  3 files changed, 76 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/git-ls-files.txt b/Documentation/git-ls-files.txt
> index b22860ec8c0..c3f46bb821b 100644
> --- a/Documentation/git-ls-files.txt
> +++ b/Documentation/git-ls-files.txt
> @@ -13,7 +13,7 @@ SYNOPSIS
>  		[-c|--cached] [-d|--deleted] [-o|--others] [-i|--|ignored]
>  		[-s|--stage] [-u|--unmerged] [-k|--|killed] [-m|--modified]
>  		[--directory [--no-empty-directory]] [--eol]
> -		[--deduplicate]
> +		[--deduplicate] [--object-only]
>  		[-x <pattern>|--exclude=<pattern>]
>  		[-X <file>|--exclude-from=<file>]
>  		[--exclude-per-directory=<file>]
> @@ -199,6 +199,12 @@ followed by the  ("attr/<eolattr>").
>  	interpolates to `\0` (NUL), `%09` to `\t` (TAB) and %0a to `\n` (LF).
>  	--format cannot be combined with `-s`, `-o`, `-k`, `--resolve-undo`,
>  	`--debug`.
> +
> +--object-only::
> +	List only names of the objects, one per line. This is equivalent
> +	to specifying `--format='%(objectname)'`. Cannot be combined with
> +	`--format=<format>`.
> +
>  \--::
>  	Do not interpret any more arguments as options.
>  
> diff --git a/builtin/ls-files.c b/builtin/ls-files.c
> index 9dd6c55eeb9..4ac8f34baac 100644
> --- a/builtin/ls-files.c
> +++ b/builtin/ls-files.c
> @@ -60,6 +60,27 @@ static const char *tag_modified = "";
>  static const char *tag_skip_worktree = "";
>  static const char *tag_resolve_undo = "";
>  
> +static enum ls_files_cmdmode {
> +	MODE_DEFAULT = 0,
> +	MODE_OBJECT_ONLY,
> +} ls_files_cmdmode;
> +
> +struct ls_files_cmdmodee_to_fmt {
> +	enum ls_files_cmdmode mode;
> +	const char *const fmt;
> +};
> +
> +static struct ls_files_cmdmodee_to_fmt ls_files_cmdmode_format[] = {
> +	{
> +		.mode = MODE_DEFAULT,
> +		.fmt = NULL,
> +	},
> +	{
> +		.mode = MODE_OBJECT_ONLY,
> +		.fmt = "%(objectname)",
> +	},
> +};
[...snip...]

This code all looks OK from skimming it, and is substantially copied
from builtin/ls-tree.c (which is good).

But I wonder as in that case whether having such an alias is worth it at
all, especially since in the case of ls-files (unlike ls-tree) we don't
start out with various --just-the-X-field type options, this is the
first one.

So I *really* like that you took my suggestion of "why not a --format"
from a previous round, but given the above for ls-files in particular is
it really worth it to have this extra code just to type:

    --object-only

Instead of:

    --format="%(objectname)"

So, maybe, and I'm not set against it, but I think it's worth
re-evaluating in this case.

In particular because the part of ls-tree's code is missing here where
we "format optimize", i.e. we take a form like:

    --format="%(objectname)"

And dispatch it to the more optimized special function, instead of the
generic strbuf_expand(), whereas in this case it's the other way around,
the option is just an alias for --format.