Universal update guide for patch versions

doc/update/patch_versions.md

+# Universal update guide for patch versions. Ex. from From 6.2.0 to 6.2.1
+
+### 0. Backup
+
+It's useful to make a backup just in case things go south:
+(With MySQL, this may require granting "LOCK TABLES" privileges to the GitLab user on the database version)
+
+```bash
+cd /home/git/gitlab
+sudo -u git -H bundle exec rake gitlab:backup:create RAILS_ENV=production
+```
+
+### 1. Stop server
+
+    sudo service gitlab stop
+
+### 2. Get latest code for your current stable branch
+
+```bash
+cd /home/git/gitlab
+sudo -u git -H git pull origin 6-2-stable
+```
+
+### 3. Install libs, migrations, etc.
+
+```bash
+cd /home/git/gitlab
+
+# MySQL
+sudo -u git -H bundle install --without development test postgres --deployment
+
+#PostgreSQL
+sudo -u git -H bundle install --without development test mysql --deployment
+
+sudo -u git -H bundle exec rake db:migrate RAILS_ENV=production
+sudo -u git -H bundle exec rake assets:clean RAILS_ENV=production
+sudo -u git -H bundle exec rake assets:precompile RAILS_ENV=production
+sudo -u git -H bundle exec rake cache:clear RAILS_ENV=production
+```
+
+### 4. Start application
+
+    sudo service gitlab start
+    sudo service nginx restart
+
+### 5. Check application status
+
+Check if GitLab and its environment are configured correctly:
+
+    sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production
+
+To make sure you didn't miss anything run a more thorough check with:
+
+    sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production
+
+If all items are green, then congratulations upgrade complete!