[PATCH] rebase: better error message when rebased changes are all in destination

[timeless]

Laurent Charignon wrote:
> +  $ hg rebase -r . -d 10
> +  abort: all selected revisions are plain prune or already exist in destination
> +  (to force the rebase, set the config experimental.rebaseskipobsolete to False)

"plain prune" isn't particularly great ...

Also, please note that `prune` isn't a term that exists in hg+rebase,
it requires another extension.

you might be able to replace "plain prune" with "obsolete"