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/share/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.

When users try to commit new changesets, a hook is run which consults the
rules file to decide whether to allow the changeset into the repository.
This can depend not only on the user and the repository, but also the
branch and files in the changeset.