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

[Taylor Blau <ttaylorr@github.com>]

On Sun, Mar 07, 2021 at 06:57:19AM +0000, ZheNing Hu via GitGitGadget wrote:
> From: ZheNing Hu <adlternative@gmail.com>
>
> 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 `--right-only`
> to range-diff, maybe can avoid this kind of mistake.
>
> Because `git rebase --apply` will internally call `git
> format-patch -k --stdout --full-index --cherry-pick --right-only
> --src-prefix=a/ --dst-prefix=b/ --no-renames --no-cover-letter
> --pretty=mboxrd --topo-order --no-base`, In order to avoid the
> ambiguity of `--right-only`, users can call `format-patch
> --range-diff --only-right` instead of `--right-only` to only emit
> output related to the second range.

A couple of times this new option is called "--right-only" and other
times it is "--only-right". This comment makes me think that you meant
to call it "--only-right", but...

> Signed-off-by: ZheNing Hu <adlternative@gmail.com>
> ---
>     [GSOC][RFC] format-patch: pass --right-only to range-diff
>
>     Transfer parameters are relatively simple. But because I can' t
>     reproduce the situation, There's no big difference between adding
>     ---only-right and not adding ---only-right. So I haven't written the
>     test files for the time being.

Note that I think (and Johannes--cc'd--could confirm) that what you want
is '--left-only' to discard rebased changes from the upstream branch:

In either case, this should help you reproduce it (and would be a good
starting point for adding a test case). Here, we're using '--left-only'
to discard changes from upstream (here, the 'main' branch) after
rebasing:

    #!/bin/sh

    set -e

    rm -fr repo
    git init repo
    cd repo

    git branch -M main

    echo "base" >base
    git add base
    git commit -m "base"

    git checkout -b my-feature
    echo "feature" >feature
    git add feature
    git commit -m "feature"

    base="$(git rev-parse main)"
    old="$(git rev-parse my-feature)"

    git checkout main
    echo "other" >>base
    git add base
    git commit -m "new"

    git checkout my-feature
    git rebase $base --onto main

    tip="$(git rev-parse my-feature)"

    git range-diff $base $old $tip
    git range-diff --left-only $base $old $tip

>     I may need to ask reviewers opinion first.
>
>     this want to fix #876 Thanks.
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-898%2Fadlternative%2Fformat-patch-range-diff-right-only-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-898/adlternative/format-patch-range-diff-right-only-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/898
>
>  Documentation/git-format-patch.txt |  5 ++++-
>  builtin/log.c                      | 15 ++++++++++-----
>  2 files changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
> index 3e49bf221087..5dae34c3090b 100644
> --- a/Documentation/git-format-patch.txt
> +++ b/Documentation/git-format-patch.txt
> @@ -27,7 +27,7 @@ SYNOPSIS
>  		   [--[no-]encode-email-headers]
>  		   [--no-notes | --notes[=<ref>]]
>  		   [--interdiff=<previous>]
> -		   [--range-diff=<previous> [--creation-factor=<percent>]]
> +		   [--range-diff=<previous> [--creation-factor=<percent>] [--right-only]]
>  		   [--filename-max-length=<n>]
>  		   [--progress]
>  		   [<common diff options>]
> @@ -301,6 +301,9 @@ material (this may change in the future).
>  	creation/deletion cost fudge factor. See linkgit:git-range-diff[1])
>  	for details.
>
> +--only-right:
> +	Used with `--range-diff`, only emit output related to the second range.
> +

s/--only-right/--right-only?

>  --notes[=<ref>]::
>  --no-notes::
>  	Append the notes (see linkgit:git-notes[1]) for the commit
> diff --git a/builtin/log.c b/builtin/log.c
> index f67b67d80ed1..5d2f39fd19a7 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -1153,7 +1153,7 @@ static void make_cover_letter(struct rev_info *rev, int use_separate_file,
>  			      struct commit *origin,
>  			      int nr, struct commit **list,
>  			      const char *branch_name,
> -			      int quiet)
> +			      int quiet, int right_only)
>  {
>  	const char *committer;
>  	struct shortlog log;
> @@ -1228,7 +1228,8 @@ static void make_cover_letter(struct rev_info *rev, int use_separate_file,
>  			.creation_factor = rev->creation_factor,
>  			.dual_color = 1,
>  			.diffopt = &opts,
> -			.other_arg = &other_arg
> +			.other_arg = &other_arg,
> +			.right_only = right_only
>  		};
>
>  		diff_setup(&opts);
> @@ -1732,7 +1733,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>  	struct strbuf rdiff2 = STRBUF_INIT;
>  	struct strbuf rdiff_title = STRBUF_INIT;
>  	int creation_factor = -1;
> -
> +	int right_only = 0;

Nit: the newline between creation_factor's declaration and
builtin_format_patch_options's is good to keep.

>  	const struct option builtin_format_patch_options[] = {
>  		OPT_CALLBACK_F('n', "numbered", &numbered, NULL,
>  			    N_("use [PATCH n/m] even with a single patch"),
> @@ -1814,6 +1815,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>  			     parse_opt_object_name),
>  		OPT_STRING(0, "range-diff", &rdiff_prev, N_("refspec"),
>  			   N_("show changes against <refspec> in cover letter or single patch")),
> +		OPT_BOOL(0, "only-right", &right_only,
> +			 N_("only emit output related to the second range")),
>  		OPT_INTEGER(0, "creation-factor", &creation_factor,
>  			    N_("percentage by which creation is weighted")),
>  		OPT_END()
> @@ -2087,7 +2090,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>  		creation_factor = RANGE_DIFF_CREATION_FACTOR_DEFAULT;
>  	else if (!rdiff_prev)
>  		die(_("--creation-factor requires --range-diff"));
> -
> +	if (right_only && !rdiff_prev)
> +		die(_("--right_only requires --range-diff"));

These may be good to combine into one big conditional that dies whenever
an option requiring --range-diff is set, but --range-diff is not:

  if (!rdiff_prev) {
    if (creation_factor)
      die(_("--creation-factor requires --range-diff"));
    if (right_only)
      die(_("--right-only requires --range-diff"));
  }

Thanks,
Taylor