enhancement🏗️good first issuepolish🪒🐃
Description
jj should have a command to sync all of my branches (or some subset) with a remote via merge or rebase, in a single operation.
Since that could cause a lot of big changes at once, it'd be nice to show a preview of changes that will be performed and prompt to confirm and/or output a very clear summary of what all changed from that sync operation.