Add environment-to-ini to docker image (#14762)

* Add environment-to-app.ini routine

* Call environment-to-ini in docker setup scripts

* Automatically convert section vars to lower case to match documentation

* Remove git patch instructions

* Add env variable documentation to Install Docker

docker/root/etc/s6/gitea/setup

@@ -48,6 +48,9 @@ if [ ! -f ${GITEA_CUSTOM}/conf/app.ini ]; then
     chown ${USER}:git ${GITEA_CUSTOM}/conf/app.ini
 fi
 
+# Replace app.ini settings with env variables in the form GITEA__SECTION_NAME__KEY_NAME
+environment-to-ini --config ${GITEA_CUSTOM}/conf/app.ini
+
 # only chown if current owner is not already the gitea ${USER}. No recursive check to save time
 if ! [[ $(ls -ld /data/gitea | awk '{print $3}') = ${USER} ]]; then chown -R ${USER}:git /data/gitea; fi
 if ! [[ $(ls -ld /app/gitea  | awk '{print $3}') = ${USER} ]]; then chown -R ${USER}:git /app/gitea;  fi

docker/rootless/usr/local/bin/docker-setup.sh

@@ -46,3 +46,6 @@ if [ ! -f ${GITEA_APP_INI} ]; then
     SECRET_KEY=${SECRET_KEY:-""} \
     envsubst < /etc/templates/app.ini > ${GITEA_APP_INI}
 fi
+
+# Replace app.ini settings with env variables in the form GITEA__SECTION_NAME__KEY_NAME
+environment-to-ini --config ${GITEA_APP_INI}