Add more notes about developer seeds

doc/development/rake_tasks.md

@@ -12,6 +12,56 @@ The `setup` task is a alias for `gitlab:setup`.
 This tasks calls `db:reset` to create the database, calls `add_limits_mysql` that adds limits to the database schema in case of a MySQL database and finally it calls `db:seed_fu` to seed the database.
 Note: `db:setup` calls `db:seed` but this does nothing.
 
+### Automation
+
+If you're very sure that you want to **wipe the current database** and refill
+seeds, you could:
+
+``` shell
+echo 'yes' | bundle exec rake setup
+```
+
+To save you from answering `yes` manually.
+
+### Discard stdout
+
+Since the script would print a lot of information, it could be slowing down
+your terminal, and it would generate more than 20G logs if you just redirect
+it to a file. If we don't care about the output, we could just redirect it to
+`/dev/null`:
+
+``` shell
+echo 'yes' | bundle exec rake setup > /dev/null
+```
+
+Note that since you can't see the questions from stdout, you might just want
+to `echo 'yes'` to keep it running. It would still print the errors on stderr
+so no worries about missing errors.
+
+### Notes for MySQL
+
+Since the seeds would contain various UTF-8 characters, such as emojis or so,
+we'll need to make sure that we're using `utf8mb4` for all the encoding
+settings and `utf8mb4_unicode_ci` for collation. Please check
+[MySQL utf8mb4 support](../install/database_mysql.md#mysql-utf8mb4-support)
+
+Make sure that `config/database.yml` has `encoding: utf8mb4`, too.
+
+Next, we'll need to update the schema to make the indices fit:
+
+``` shell
+sed -i 's/limit: 255/limit: 191/g' db/schema.rb
+```
+
+Then run the setup script:
+
+``` shell
+bundle exec rake setup
+```
+
+To make sure that indices still fit. You could find great details in:
+[How to support full Unicode in MySQL databases](https://mathiasbynens.be/notes/mysql-utf8mb4)
+
 ## Run tests
 
 In order to run the test you can use the following commands: