Sysadmin documentation is unclear about Git repositories for Puppet code

In particular, https://tails.boum.org/contribbute/working_together/roles/sysadmins/ does not mention where the puppet stuff actually lives nor the synchronisation that goes on between immerda and git.puppet.tails.boum.org

Original created by @groente on 14613 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information