Alex Henrie [off-list ref] writes:

The purpose of the new option is to accommodate users who would like
--rebase-merges to be on by default and to facilitate turning on
--rebase-merges by default without configuration in a future version of
Git.

Name the new option rebase.rebaseMerges, even though it is a little
redundant, for consistency with the name of the command line option and
to be clear when scrolling through values in the [rebase] section of
.gitconfig.

This rationale makes sense to me.

In the future, the default rebase-merges mode may change from
no-rebase-cousins to rebase-cousins.

I suspect a more likely future would be that the default is to rebase
'evil' merges instead of trying to recreate merge commits, but of
course, the important thing is that we promote the default, not what the
default will be...

                                     Support setting rebase.rebaseMerges
to the nonspecific value "true" for users who do not need or want to
care about the default changing in the future. Similarly, for users who
have --rebase-merges in an alias and want to get the future behavior
now, use the specific rebase-merges mode from the config if a specific
mode is not given on the command line.

so this rationale makes sense to me too :)

I believe this used to be on 2/3, i.e.

  https://lore.kernel.org/git/20230225180325.796624-3-alexhenrie24@gmail.com/ (local)

but your cover letter suggests that it was removed. Mechanical error?

The rest of changes look good (besides what others have spotted).