This hook can be used as a pretxnchangegroup hook in order to ensure only changesets are pushed which are signed with GnuPG using the GpgExtension. To be more specific, the script makes sure all heads of the changesets to push are signed and have a valid signature.

Just ensure the following entry is contained within the repository's hgrc file:

[hooks]
pretxnchangegroup.checkgpgsig = python:hghooklib.checkgpgsig.hook