Feature Request: Branch Description updating support for git fetch/pull/push

Branch descriptions are great. Even more so if you set merge.branchdesc=true (while we are at it could there be a CLI option to git merge that allowed overriding merge.branchdesc for that merge)

But the bit that pains me is that my description is local only.

Could we add support for syncing the branch description with the remote?

When I think about how such sync could work:

* I would see the sync as an option that needs to be enabled rather
than on by default (at least as long as `merge.branchdesc` is an
option). Overriding by the CLI would be great, e.g.
`--description-sync / --no-description-sync`
* When that sync is enabled, if the destination side is missing a
description then the description is sync'd. Otherwise if the
destination description differs from the source description the user
must explicitly specify one of `--description-sync /
--no-description-sync` or else the operation will stop before updating
references (I think that `git fetch` could be an exception to this
rule as updating the remote branch descriptions by overwriting is
exactly what you want, but for `git pull` / `git push` I think they
need the CLI confirmation if the user has opted into synchronizing
branch descriptions)

WDYT?