[PATCH 1 of 2] split: new extension to split changesets

[Martin von Zweigbergk]

On Sat, Jun 24, 2017 at 10:45 PM, Jun Wu <quark at fb.com> wrote:
> + at command('^split',
> +    [('r', 'rev', '', _("revision to split"), _('REV')),
> +     ('', 'no-rebase', False, _('do not rebase descendants after split')),
> +    ] + cmdutil.commitopts2,

The default of False probably deserves a separate discussion.

When allowunstable is not enabled, I think other commands ("commit
--amend", "rebase", "histedit") currently simply fail if there are
descendants of the rewritten commit, so we could make them rebase
instead without breaking BC too much (not error out anymore is usually
fine).

When allowunstable *is* enabled, none of "hg commit --amend", "hg
rebase", and "hg histedit" currently rebase by default. Unless we
decide that we should change their defaults, I don't see why the
default of "hg split" should be different. It's probably okay to
change the default of those commands given that evolve is still
experimental? (Although evolve is not required for using
allowunstable, I'd be surprised if users set allowunstable without
evolve enabled.)