HOW IT WORKS

When a developer attempts to connect to a repository via ssh, the SSH daemon
searches for a match for that user's key in ~hg/.ssh/authorized_keys. If the
developer is authorised to connect to the repository they will have an entry
in this file. The entry includes a "command" prefix which specifies that the
restricted shell "/usr/local/lib/mercurial-server/hg-ssh" should be used; this
shell is passed an argument identifying the developer. The shell parses the
command the developer is trying to execute, and consults a rules file to see
if that developer is allowed to perform that action on that repository.

The file ~hg/.ssh/authorized_keys is generated by "refresh-auth", which
recurses through two directories of files containing SSH keys and generates an
entry in authorized_keys for each one, using the name of the key file as the
identifier for the developer. These keys will live in the "keys" subdirectory
"/etc/mercurial-server" and the "keys" subdirectory of a repository called
"hgadmin". A hook in this repository re-runs "refresh-auth" on the most recent
version after every push.

Finally, hook in an extension is run for each changeset that is remotely
committed, which uses the rules file to determine whether to allow the
changeset.