Today the standard way to fetch a reflog from a git server is to
find the repository and cat the appropriate file from .git/logs,
or to run "git log -g" on the server.  Server admins that don't offer
SSH access have to find some other, custom way to communicate the
reflog out of band.

It would be nice if there were a standard command similar to git
upload-pack and git upload-archive that, when enabled, could send back
reflogs in a standard format.

This would also be a good place to put the push certificates for
servers that have enabled that feature (so the fetcher could verify
that the reflog is accurate).