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Re: [PATCH v2 2/3] update-index: add --show-index-version

From
LALinus Arver <linusa@google.com>
Date
Sep 12, 2023, 05:54 UTC
Message-ID
<owlybke8kkcf.fsf@fine.c.googlers.com>
In-Reply-To
<20230818233729.2766281-3-gitster@pobox.com>
Junio C Hamano <gitster@pobox.com> writes:
> "git update-index --version N" is used to set the index format
s/--version/--index-version
Show 24 quoted lines
> version to a specific version, but there was no way to query the
> current version used in the on-disk index file.
>
> Teach the command a new "--show-index-version" option, and also
> teach the "--index-version N" option to report what the version was
> when run with the "--verbose" option.
>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  Documentation/git-update-index.txt |  6 +++++-
>  builtin/update-index.c             | 19 +++++++++++++------
>  t/t2107-update-index-basic.sh      | 16 ++++++++++++++++
>  3 files changed, 34 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/git-update-index.txt b/Documentation/git-update-index.txt
> index a367f8d65a..3f204891ce 100644
> --- a/Documentation/git-update-index.txt
> +++ b/Documentation/git-update-index.txt
> @@ -162,7 +162,8 @@ you will need to handle the situation manually.
>  	Write the resulting index out in the named on-disk format version.
>  	Supported versions are 2, 3 and 4. The current default version is 2
>  	or 3, depending on whether extra features are used, such as
> -	`git add -N`.
> +	`git add -N`.  With `--verbose` option, also reports the
How about
    `git add -N`.  With `--verbose`, also report the
Show 11 quoted lines
> +	version the index file uses before and after this command.
>  +
>  Version 4 performs a simple pathname compression that reduces index
>  size by 30%-50% on large repositories, which results in faster load
> @@ -171,6 +172,9 @@ and support for it was added to libgit2 in 2016 and to JGit in 2020.
>  Older editions of this manual page called it "relatively young", but
>  it should be considered mature technology these days.
>
> +--show-index-version::
> +	Report the index format version used by the on-disk index file.
> +	See `--index-version` above.
Looks good.
Show 12 quoted lines
>  -z::
>  	Only meaningful with `--stdin` or `--index-info`; paths are
> diff --git a/builtin/update-index.c b/builtin/update-index.c
> index 5fab9ad2ec..e713e2a04c 100644
> --- a/builtin/update-index.c
> +++ b/builtin/update-index.c
> @@ -1089,6 +1089,8 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
>  			resolve_undo_clear_callback),
>  		OPT_INTEGER(0, "index-version", &preferred_index_format,
>  			N_("write index in this format")),
> +		OPT_SET_INT(0, "show-index-version", &preferred_index_format,
> +			    N_("show index format version"), -1),
How about
    "show on-disk index format version"

for the help text? Also "report" may be preferable instead of "show" for consistency with the manpage.

Also, I think it would be easier to read if we didn't overload preferred_index_format here and instead used a new variable (perhaps named "show_index_format").

And I just realized that we are now using not only "show" and "report" interchangeably in this patch, but also "format" and "version" --- it would be nice to clean up as #leftoverbits.

Show 28 quoted lines
>  		OPT_BOOL(0, "split-index", &split_index,
>  			N_("enable or disable split index")),
>  		OPT_BOOL(0, "untracked-cache", &untracked_cache,
> @@ -1181,15 +1183,20 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
>
>  	getline_fn = nul_term_line ? strbuf_getline_nul : strbuf_getline_lf;
>  	if (preferred_index_format) {
> -		if (preferred_index_format < INDEX_FORMAT_LB ||
> -		    INDEX_FORMAT_UB < preferred_index_format)
> +		if (preferred_index_format < 0) {
> +			printf(_("%d\n"), the_index.version);
> +		} else if (preferred_index_format < INDEX_FORMAT_LB ||
> +			   INDEX_FORMAT_UB < preferred_index_format) {
>  			die("index-version %d not in range: %d..%d",
>  			    preferred_index_format,
>  			    INDEX_FORMAT_LB, INDEX_FORMAT_UB);
> -
> -		if (the_index.version != preferred_index_format)
> -			the_index.cache_changed |= SOMETHING_CHANGED;
> -		the_index.version = preferred_index_format;
> +		} else {
> +			if (the_index.version != preferred_index_format)
> +				the_index.cache_changed |= SOMETHING_CHANGED;
> +			report(_("index-version: was %d, set to %d"),
> +			       the_index.version, preferred_index_format);
> +			the_index.version = preferred_index_format;
> +		}
>  	}

Looks good. But if you decide to use a new variable like "show_index_format" as suggested above, you might want to refactor this out to a separate function. Then you could obviously do away with the chained if/else and replace them with early returns, which would be easier to read.

Show 12 quoted lines
>  	if (read_from_stdin) {
> diff --git a/t/t2107-update-index-basic.sh b/t/t2107-update-index-basic.sh
> index 89b285fa3a..c78d1e9396 100755
> --- a/t/t2107-update-index-basic.sh
> +++ b/t/t2107-update-index-basic.sh
> @@ -111,4 +111,20 @@ test_expect_success '--chmod=+x and chmod=-x in the same argument list' '
>  	test_cmp expect actual
>  '
>
> +test_expect_success '--index-version' '
> +	git commit --allow-empty -m snap &&
> +	git reset --hard &&

Not sure why this "git reset --hard" is needed here --- is it to clear out state from previous test cases? If so, perhaps it's better to run this as the very first command in this test case?

But this also makes me wonder why "git commit --allow-empty -m snap" is even necessary (if we already have a git repo)?

> +	git update-index --index-version 2 >actual &&
> +	test_must_be_empty actual &&

Before we do "--index-version 2", it may be desirable to run the "--show-index-version" flag first to see what we have before modifying it with "2".

Show 8 quoted lines
> +	git update-index --show-index-version >actual &&
> +	echo 2 >expect &&
> +	test_cmp expect actual &&
> +
> +	git update-index --index-version 4 --verbose >actual &&
> +	echo "index-version: was 2, set to 4" >expect &&
> +	test_cmp expect actual
> +'

How about adding this check below to check what happens if the newly-set version is the same as the existing version?

        git update-index --index-version 4 --verbose >actual &&
        echo "index-version: was 4, set to 4" >expect &&
        test_cmp expect actual

And also how about a similar check, but for downgrading from a higher version number to a lower one?

        git update-index --index-version 2 --verbose >actual &&
        echo "index-version: was 4, set to 2" >expect &&
        test_cmp expect actual
> +
>  test_done
> --
> 2.42.0-rc2-7-gf9972720e9
Previous: Junio C HamanoNext: Junio C Hamano
Message 6 of 17 in “"update-index --show-index-version"”
  1. 0/3 "update-index --show-index-version"Junio C Hamano, Aug 18, 2023
  2. 1/3 update-index doc: v4 is OK with JGit and libgit2Junio C Hamano, Aug 18, 2023
  3. Linus ArverSep 12, 2023
  4. Junio C HamanoSep 12, 2023
  5. 2/3 update-index: add --show-index-versionJunio C Hamano, Aug 18, 2023
  6. Linus ArverSep 12, 2023
  7. Junio C HamanoSep 12, 2023
  8. 3/3 test-tool: retire "index-version"Junio C Hamano, Aug 18, 2023
  9. Linus ArverSep 12, 2023
  10. 0/3 "update-index --show-index-version"Junio C Hamano, Sep 12, 2023
  11. 1/3 update-index doc: v4 is OK with JGit and libgit2Junio C Hamano, Sep 12, 2023
  12. 2/3 update-index: add --show-index-versionJunio C Hamano, Sep 12, 2023
  13. 2/3 update-index: add --show-index-versionTeng Long, Nov 14, 2023
  14. Junio C HamanoNov 14, 2023
  15. 3/3 test-tool: retire "index-version"Junio C Hamano, Sep 12, 2023
  16. Linus ArverSep 14, 2023
  17. Junio C HamanoSep 14, 2023

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