Subject: Re: [PATCH v3 1/1] upload-pack.c: fix filter spec quoting bug

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Tue, 26 Jan 2021 10:57:36 +0100

On Tue, Jan 26 2021, Jacob Vosmaer wrote:

> This fixes a bug that occurs when you combine partial clone and
> uploadpack.packobjectshook. You can reproduce it as follows:

Let's: 

 * Refer to the commit we're fixing a bug in, i.e. Junio's mention of
   10ac85c7 (upload-pack: add object filtering for partial clone,
   2017-12-08) upthread.

 * See also "imperative-mood" in SubmittingPatches. I.e. say "Fix a bug
   in ..." not "This fixes ... can be reproduced as"

 * uploadpack.packObjectsHook not uploadpack.packobjectshook except in C
   code.

> git clone -u 'git -c uploadpack.allowfilter '\
> '-c uploadpack.packobjectshook=env '\
> 'upload-pack' --filter=blob:none --no-local \
> src.git dst.git

This and the output below would be more readable indented.

> Be careful with the line endings because this has a long quoted string
> as the -u argument.
>
> The error I get when I run this is:
>
> Cloning into '/tmp/broken'...
> remote: fatal: invalid filter-spec ''blob:none''
> error: git upload-pack: git-pack-objects died with error.
> fatal: git upload-pack: aborting due to possible repository corruption on the remote side.
> remote: aborting due to possible repository corruption on the remote side.
> fatal: early EOF
> fatal: index-pack failed

[...]

> The problem is an unnecessary and harmful layer of quoting. I tried
> digging through the history of this function and I think this quoting
> was there from the start.

...So looked at "git log" but didn't try to check out 10ac85c7 and see
if it had the same issue? If we're going to leave a note about this at
all probably better to help future source spelunkers by being able to
say the issue was there from the start.

> My best guess is that it stems from a
> misunderstanding what use_shell=1 means. The code seems to assume it
> means "arguments get joined into one big string, then fed to /bin/sh".
> But that is not what it means: use_shell=1 means that the first
> argument in the arguments array may be a shell script and if so should
> be passed to /bin/sh. All other arguments are passed as normal
> arguments.
>
> The solution is simple: never quote the filter spec.
>
> This commit removes the conditional quoting and adds a test for
> partial clone in t5544.
>

Thanks for hacking this up! Hopefully the above is helpful and not too
nitpicky. Mainly wanted to help you get future patches through more
easily...

> Signed-off-by: Jacob Vosmaer <[email-masked]>
> ---
>  t/t5544-pack-objects-hook.sh | 9 +++++++++
>  upload-pack.c                | 9 +--------
>  2 files changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/t/t5544-pack-objects-hook.sh b/t/t5544-pack-objects-hook.sh
> index 4357af1525..f5ba663d64 100755
> --- a/t/t5544-pack-objects-hook.sh
> +++ b/t/t5544-pack-objects-hook.sh
> @@ -59,4 +59,13 @@ test_expect_success 'hook does not run from repo config' '
>  	test_path_is_missing .git/hook.stdout
>  '
>  
> +test_expect_success 'hook works with partial clone' '
> +	clear_hook_results &&
> +	test_config_global uploadpack.packObjectsHook ./hook &&
> +	test_config_global uploadpack.allowFilter true &&
> +	git clone --bare --no-local --filter=blob:none . dst.git &&
> +	git -C dst.git rev-list --objects --missing=print HEAD >objects &&
> +	grep "^?" objects
> +'
> +
>  test_done
> diff --git a/upload-pack.c b/upload-pack.c
> index 3b66bf92ba..eae1fdbc55 100644
> --- a/upload-pack.c
> +++ b/upload-pack.c
> @@ -305,14 +305,7 @@ static void create_pack_file(struct upload_pack_data *pack_data,
>  	if (pack_data->filter_options.choice) {
>  		const char *spec =
>  			expand_list_objects_filter_spec(&pack_data->filter_options);
> -		if (pack_objects.use_shell) {
> -			struct strbuf buf = STRBUF_INIT;
> -			sq_quote_buf(&buf, spec);
> -			strvec_pushf(&pack_objects.args, "--filter=%s", buf.buf);
> -			strbuf_release(&buf);
> -		} else {
> -			strvec_pushf(&pack_objects.args, "--filter=%s", spec);
> -		}
> +		strvec_pushf(&pack_objects.args, "--filter=%s", spec);
>  	}
>  	if (uri_protocols) {
>  		for (i = 0; i < uri_protocols->nr; i++)