Re: [PATCH v2] [GSOC][RFC] format-patch: pass --left-only to range-diff

[Eric Sunshine <sunshine@xxxxxxxxxxxxx>]

On Tue, Mar 9, 2021 at 3:35 AM ZheNing Hu via GitGitGadget
<gitgitgadget@xxxxxxxxx> wrote:
> In https://lore.kernel.org/git/YBx5rmVsg1LJhSKN@nand.local/,
> Taylor Blau proposing `git format-patch --cover-letter
> --range-diff` may mistakenly place upstream commit in the
> range-diff output. Teach `format-patch` pass `--left-only`
> to range-diff,can avoid this kind of mistake.
>
> Signed-off-by: ZheNing Hu <adlternative@xxxxxxxxx>
> ---
> diff --git a/builtin/log.c b/builtin/log.c
> @@ -2085,9 +2089,12 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>         if (creation_factor < 0)
>                 creation_factor = RANGE_DIFF_CREATION_FACTOR_DEFAULT;
> -       else if (!rdiff_prev)
> -               die(_("--creation-factor requires --range-diff"));
> -
> +       else if (!rdiff_prev) {
> +               if (creation_factor >= 0)
> +                       die(_("--creation-factor requires --range-diff"));
> +               if (left_only)
> +                       die(_("--left-only requires --range-diff"));
> +       }

This logic starts getting difficult to reason about. It would be
easier to understand if written like this:

    if (!rdiff_prev) {
        if (creation_factor >= 0)
            die(_("--creation-factor requires --range-diff"));
        if (left_only)
            die(_("--left-only requires --range-diff"));
    }

    if (creation_factor < 0)
        creation_factor = RANGE_DIFF_..._DEFAULT;

or this (which reduces the indentation a bit):

    if (creation_factor >= 0 && !rdiff_prev)
        die(_("--creation-factor requires --range-diff"));
    if (left_only && !rdiff_prev)
        die(_("--left-only requires --range-diff"));

    if (creation_factor < 0)
        creation_factor = RANGE_DIFF_..._DEFAULT;

Subjective; not necessarily worth a re-roll.

> @@ -2134,7 +2141,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>                 make_cover_letter(&rev, !!output_directory,
> -                                 origin, nr, list, branch_name, quiet);
> +                                 origin, nr, list, branch_name, quiet,
> +                                       left_only);

Nit: This indentation looks odd. One would expect `origin` and
`left_only` to have the same indentation.

> diff --git a/t/t3206-range-diff.sh b/t/t3206-range-diff.sh
> @@ -748,4 +748,32 @@ test_expect_success '--left-only/--right-only' '
> +test_expect_success 'format-patch --range-diff --left-only' '
> +       rm -fr repo &&
> +       git init repo &&
> +       ...
> +       ! grep  "> 1: .* feature$"  0000-cover-letter.patch
> +'
> +
> +
>  test_done

Nit: One blank line before test_done() is typical, not two.