expand on old git repositories situation

howto/git.md

@@ -432,6 +432,16 @@ servers. Those are:
  - Passwords, moved to `pauli`:
    * `tor-passwords`: password manager
 
+When the repositories required some action to happen on push (which is
+all repositories except the password manager), a `post-receive` hook
+was implemented to match the original configuration.
+
+They are all actual git repositories with working trees (as opposed to
+bare repositories) to simplify the configuration (and avoid an
+intermediate bare repository). Local changes are strongly discouraged,
+the work tree is updated thanks to the
+`receive.denyCurrentBranch=updateInstead` configuration setting.
+
 ## Destroying a repository
 
 Instead of migrating a repository to GitLab, you might want to simply