Add instructions on manually rebuilding a branch

README.md

@@ -2,7 +2,7 @@ This repository contains scripts for automatically building the Python
 documentation on [docs.python.org](https://docs.python.org).
 
 
-# How to test it?
+## How to test it?
 
 The following command should build all maintained versions and
 translations in `./www`, beware it can take a few hours:
@@ -15,7 +15,7 @@ If you don't need to build all translations of all branches, add
 `--language en --branch main`.
 
 
-# Check current version
+## Check current version
 
 Install `tools_requirements.txt` then run `python check_versions.py
 ../cpython/` (pointing to a real CPython clone) to see which version
@@ -51,3 +51,20 @@ of Sphinx we're using where:
     3.13       8.1.3  8.1.3  8.1.3  8.1.3  8.1.3  8.1.3  8.1.3  8.1.3  8.1.3    8.1.3  8.1.3  8.1.3    8.1.3
     3.14       8.1.3  8.1.3  8.1.3  8.1.3  8.1.3  8.1.3  8.1.3  8.1.3  8.1.3    8.1.3  8.1.3  8.1.3    8.1.3
     =========  =====  =====  =====  =====  =====  =====  =====  =====  =======  =====  =====  =======  =======
+
+## Manually rebuild a branch
+
+Docs for [feature and bugfix branches](https://devguide.python.org/versions/) are
+automatically built from a cron.
+
+Manual rebuilds are needed for new security releases,
+and to add the end-of-life banner for newly end-of-life branches.
+
+To manually rebuild a branch, for example 3.11:
+
+```shell
+ssh docs.nyc1.psf.io
+sudo su --shell=/bin/bash docsbuild
+screen -DUR  # Rejoin screen session if it exists, otherwise create a new one
+/srv/docsbuild/venv/bin/python /srv/docsbuild/scripts/build_docs.py --branch 3.11
+```