I have finally managed to set up a dedicated Git server.

The URL to gitweb is: https://git.gameoftrees.org/

The following can be used to clone the reference repository directly:

  git clone https://git.gameoftrees.org/got.git
  git clone git://git.gameoftrees.org/got.git

The repository clone at framagit will remain available as a mirror.

Developers with SSH access will receive instructions on how to access
the new server soon (write access to the old server has already been
disabled).