Hi Phillip,
On Tue, Jan 24, 2023 at 5:16 AM Phillip Wood <phillip.wood123@xxxxxxxxx> wrote:
>
> >>>> Signed-off-by: Elijah Newren <newren@xxxxxxxxx>
> >>>> --- a/builtin/rebase.c
> >>>> +++ b/builtin/rebase.c
> >>>> @@ -1224,6 +1224,26 @@ int cmd_rebase(int argc, const char **argv,
> >>>> const char *prefix)
> >>>> if (options.fork_point < 0)
> >>>> options.fork_point = 0;
> >>>> }
> >>>> + /*
> >>>> + * The apply backend does not support
> >>>> --[no-]reapply-cherry-picks.
> >>>> + * The behavior it implements by default is equivalent to
> >>>> + * --no-reapply-cherry-picks (due to passing --cherry-picks to
> >>>> + * format-patch), but --keep-base alters the upstream such
> >>>> that no
> >>>> + * cherry-picks can be found (effectively making it act like
> >>>> + * --reapply-cherry-picks).
> >>>> + *
> >>>> + * Now, if the user does specify --[no-]reapply-cherry-picks, but
> >>>> + * does so in such a way that options.reapply_cherry_picks ==
> >>>> + * keep_base, then the behavior they get will match what they
> >>>> + * expect despite options.reapply_cherry_picks being ignored. We
> >>>> + * could just allow the flag in that case, but it seems better to
> >>>> + * just alert the user that they've specified a flag that the
> >>>> + * backend ignores.
> >>>> + */
> >>>
> >>> I'm a bit confused by this. --keep-base works with either
> >>> --reapply-cherry-picks (which is the default if --keep-base is given) or
> >>> --no-reapply-cherry-picks. Just below this hunk we have
> >>>
> >>> if (options.reapply_cherry_picks < 0)
> >>> options.reapply_cherry_picks = keep_base;
> >>>
> >>> So we only set options.reapply_cherry_picks to match keep_base if the
> >>> user did not specify -[-no]-reapply-cherry-picks on the commandline.
> >>
> >> options.reapply_cherry_picks is totally ignored by the apply backend,
> >> regardless of whether it's set by the user or the setup code in
> >> builtin/rebase.c. And if we have an option which is ignored, isn't it
> >> nicer to provide an error message to the user if they tried to set it?
> >>
> >> Said another way, while users could start with these command lines:
> >>
> >> (Y) git rebase --whitespace=fix
> >> (Z) git rebase --whitespace=fix --keep-base
> >>
> >> and modify them to include flags that would be ignored, we could allow:
> >>
> >> (A) git rebase --whitespace=fix --no-reapply-cherry-picks
> >> (B) git rebase --whitespace=fix --keep-base --reapply-cherry-picks
> >>
> >> But we could not allow commands like
> >>
> >> (C) git rebase --whitespace=fix --reapply-cherry-picks
> >> (D) git rebase --whitespace=fix --keep-base
> >> --no-reapply-cherry-picks
> >
> > (C) is already an error
> > (D) is currently allowed and I think works as expected (--keep-base only
> > implies --reapply-cherry-picks, the user is free to override that with
> > --no-reapply-cherry-picks) so I don't see why we'd want to make it an
> > error.
Ah, despite looking over the code multiple times to check my
statements, I somehow kept missing this:
if (keep_base && options.reapply_cherry_picks)
options.upstream = options.onto;
which is how --[no-]reapply-cherry-picks is supported in conjunction
with --keep-base. Thanks.
> >> For all four cases (A)-(D), the apply backend will ignore whatever
> >> --[no-]reapply-cherry-picks flag is provided.
> >
> > For (D) the flag is respected, (C) errors out, the other cases
> > correspond to the default so it's like saying
> >
> > git rebase --merge --no-reapply-cherry-picks
> >
> > ignores the flag.
>
> On reflection that is only true for (B). I agree that we should error
> out on (A) which we don't at the moment.
>
> I'd support a change that errors out on (A) and (C) but continues to
> allow (B) and (D). I think we can do that with the diff below
>
>
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 1481c5b6a5..66aef356b8 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -1230,12 +1230,6 @@ int cmd_rebase(int argc, const char **argv, const
> char *prefix)
> if (options.fork_point < 0)
> options.fork_point = 0;
> }
> - /*
> - * --keep-base defaults to --reapply-cherry-picks to avoid losing
> - * commits when using this option.
> - */
> - if (options.reapply_cherry_picks < 0)
> - options.reapply_cherry_picks = keep_base;
>
> if (options.root && options.fork_point > 0)
> die(_("options '%s' and '%s' cannot be used
> together"), "--root", "--fork-point");
> @@ -1412,11 +1406,17 @@ int cmd_rebase(int argc, const char **argv,
> const char *prefix)
> if (options.empty != EMPTY_UNSPECIFIED)
> imply_merge(&options, "--empty");
>
> - /*
> - * --keep-base implements --reapply-cherry-picks by altering
> upstream so
> - * it works with both backends.
> - */
> - if (options.reapply_cherry_picks && !keep_base)
> + if (options.reapply_cherry_picks < 0)
> + /*
> + * --keep-base defaults to --reapply-cherry-picks to
> + * avoid losing commits when using this option.
> + */
I know you were copying the previous comment, but this comment is
really confusing to me. Shouldn't it read "--reapply-cherry-picks
defaults to --keep-base" instead of vice-versa?
> + options.reapply_cherry_picks = keep_base;
> + else if (!keep_base)
> + /*
> + * --keep-base implements --reapply-cherry-picks by
Should this be --[no-]reapply-cherry-picks, to clarify that it handles
both cases? Especially given how many times I missed it?
> + * altering upstream so it works with both backends.
> + */
> imply_merge(&options, "--reapply-cherry-picks");
And perhaps this should be
imply_merge(&options, options.reapply_cherry_picks ?
"--reapply-cherry-picks" :
"--no-reapply-cherry-picks");
Also, the comment in git-rebase.txt about incompatibilities would become
* --[no-]reapply-cherry-picks, when --keep-base is not provided
