Use tags to do minor updates of GitLab

doc/update/patch_versions.md

@@ -18,10 +18,11 @@ sudo -u git -H bundle exec rake gitlab:backup:create RAILS_ENV=production
 
 ```bash
 cd /home/git/gitlab
-sudo -u git -H git pull origin STABLE_BRANCH
+sudo -u git -H git fetch --all
+sudo -u git -H git checkout LATEST_TAG
 ```
 
-Replace STABLE_BRANCH with the minor version you want to upgrade to, for example `6-3-stable`.
+Replace LATEST_TAG with the latest GitLab tag you want to upgrade to, for example `v6.6.3`.
 
 ### 3. Update gitlab-shell if it is not the latest version