doc: add update documentation

Fixes #244

doc/index.rst

@@ -18,6 +18,7 @@ Demo: https://pytitiondemo.sionneau.net/
 
    installation
    configuration
+   update
 
 
 Indices and tables

doc/update.rst

@@ -0,0 +1,82 @@
+Update
+******
+
+Backup your files
+=================
+
+Backup your media files, those are the pictures uploaded by your users in the petition contents and metadata.
+
+The files to backup are in the mediaroot directory that you configured in your settings in the `MEDIA_ROOT` variable.
+
+.. code-block::
+
+    $ source path/to/pytition_venv/bin/activate
+    $ export DJANGO_SETTINGS_MODULE="pytition.settings.config" # path to your config
+    $ backup_dir=pytition_backup_$(date +%Y%m%d_%H%M%S)
+    $ mediaroot_dir=$(python3 pytition/manage.py shell -c 'from django.conf import settings; print(settings.MEDIA_ROOT)')
+    $ rsync -av $mediaroot_dir $backup_dir
+
+Backup your Database
+====================
+
+For this, I would advise to use the tools provided with your database server.
+
+* SQLite: just copy your .db file and you're done!
+* PostgreSQL: use `pg_dump` to backup and `psql` to restore
+* MariaDB / MySQL: use `mysqldump` to backup and `mysql` to restore
+
+You can also try to backup using the django tool:
+
+.. code-block::
+
+    $ source path/to/pytition_venv/bin/activate
+    $ export DJANGO_SETTINGS_MODULE="pytition.settings.config" # path to your config
+    $ # let's dump data
+    $ python3 pytition/manage.py dumpdata --all --output data.json
+    $ # now let's restore it
+    $ python3 pytition/manage.py loaddata data.json
+
+.. warning::
+
+    Always *test* your backup mechanism. If not tested, you can only suppose your backups are worthless.
+    You need to try to restore them on a dummy and empty instance, in order to make sure the backup is OK.
+    Untested backups do not work.
+
+Update to a newer Pytition version
+==================================
+
+You can simply run the `update` command of the `manage.py` CLI:
+
+.. code-block::
+
+    $ source pytition_venv/bin/activate
+    $ python3 pytition/manage.py update
+
+Or go through the following document and do it manually.
+
+Download latest Pytition release tarball or update your git clone:
+
+.. code-block::
+
+    $ git stash && git pull
+    $ version=$(curl -s https://api.github.com/repos/pytition/pytition/releases/latest | grep "tag_name" | cut -d : -f2,3 | tr -d \" | tr -d ,)
+    $ git checkout $version
+
+Then upgrade Pytition's dependencies:
+
+.. code-block::
+
+    $ source pytition_venv/bin/activate
+    (pytition_venv) $ pip3 install --upgrade -r requirements.txt
+
+Then update your database scheme, update static files, compile new translation files:
+
+.. code-block::
+
+    $ export DJANGO_SETTINGS_MODULE="pytition.settings.config" # path to your config
+    $ python3 pytition/manage.py migrate
+    $ python3 pytition/manage.py collectstatic
+    $ python3 pytition/manage.py compilemessages
+
+Then restart your web server, be it apache or nginx, and also your application server (uWSGI).
+Congratulations! You should now be OK with a brand new Pytition release!