Re: [PATCH 1/3] t7610-mergetool: do not place pipelines headed by `yes` in subshells

From: SZEDER Gábor <szeder.dev@gmail.com>
Date: Jun 10, 2019, 09:59 UTC
Message-ID: <20190610095942.GA19035@szeder.dev>
In-Reply-To: <75c812bd4838f6f35b6f42b97ae396ebb28d8b95.1560152205.git.j6t@kdbg.org>

On Mon, Jun 10, 2019 at 10:58:58AM +0200, Johannes Sixt wrote:

Show 8 quoted lines

> Subshells for pipelines are not required. This can save a number of
> processes (if the shell does not optimize it away anyway).
> 
> The patch was generated with the command
> 
>    sed -i 's/( *\(yes.*[^ ]\) *) *\&\&/\1 \&\&/' t7610-mergetool.sh
> 
> with a manual fixup of the case having no && at the end.

I think it would be great to include the corresponding numbers from the cover letter in each of the commit messages.

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> Signed-off-by: Johannes Sixt <j6t@kdbg.org>
> ---
>  t/t7610-mergetool.sh | 170 +++++++++++++++++++++----------------------
>  1 file changed, 85 insertions(+), 85 deletions(-)
> 
> diff --git a/t/t7610-mergetool.sh b/t/t7610-mergetool.sh
> index 5b61c10a9c..b67440882b 100755
> --- a/t/t7610-mergetool.sh
> +++ b/t/t7610-mergetool.sh
> @@ -131,13 +131,13 @@ test_expect_success 'custom mergetool' '
>  	git checkout -b test$test_count branch1 &&
>  	git submodule update -N &&
>  	test_must_fail git merge master &&
> -	( yes "" | git mergetool both ) &&
> -	( yes "" | git mergetool file1 file1 ) &&
> -	( yes "" | git mergetool file2 "spaced name" ) &&
> -	( yes "" | git mergetool subdir/file3 ) &&
> -	( yes "d" | git mergetool file11 ) &&
> -	( yes "d" | git mergetool file12 ) &&
> -	( yes "l" | git mergetool submod ) &&
> +	yes "" | git mergetool both &&
> +	yes "" | git mergetool file1 file1 &&
> +	yes "" | git mergetool file2 "spaced name" &&
> +	yes "" | git mergetool subdir/file3 &&
> +	yes "d" | git mergetool file11 &&
> +	yes "d" | git mergetool file12 &&
> +	yes "l" | git mergetool submod &&
>  	test "$(cat file1)" = "master updated" &&
>  	test "$(cat file2)" = "master new" &&
>  	test "$(cat subdir/file3)" = "master new sub" &&

Another possibility for eliminating a few more subshells might be to turn these

  test "$(cat file1)" = "that"'

checks into

  echo that >expect &&
  test_cmp expect file1

because 'test_cmp' on Windows first compares the two files in shell and runs 'diff' only when there is a difference to report.