Add a combined update doc from 5.1 to 6.0

doc/update/5.1-to-6.0.md

+# From 5.1 to 6.0
+
+### Deprecations
+
+#### Global projects
+
+The root (global) namespace for projects is deprecated.
+So you need to move all your global projects under groups or users manually before update or they will be automatically moved to the project owner namespace during the update. When a project is moved all its members will receive an email with instructions how to update their git remote url. Please make sure you disable sending email when you do a test of the upgrade.
+
+#### Teams
+
+We introduce group membership in 6.0 as a replacement for teams.
+The old combination of groups and teams was confusing for a lot of people.
+And when the members of a team where changed this wasn't reflected in the project permissions.
+In GitLab 6.0 you will be able to add members to a group with a permission level for each member.
+These group members will have access to the projects in that group.
+Any changes to group members will immediately be reflected in the project permissions.
+You can even have multiple owners for a group, greatly simplifying administration.
+
+### 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
+
+```bash
+cd /home/git/gitlab
+sudo -u git -H git fetch
+sudo -u git -H git checkout 6-0-stable
+```
+
+### 3. Update gitlab-shell
+
+```bash
+cd /home/git/gitlab-shell
+sudo -u git -H git fetch
+sudo -u git -H git checkout v1.7.0
+```
+
+### 4. Install additional packages
+
+```bash
+# For reStructuredText markup language support install required package:
+sudo apt-get install python-docutils
+```
+
+### 5. 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 migrate_groups RAILS_ENV=production
+sudo -u git -H bundle exec rake migrate_global_projects RAILS_ENV=production
+sudo -u git -H bundle exec rake migrate_keys RAILS_ENV=production
+sudo -u git -H bundle exec rake migrate_inline_notes RAILS_ENV=production
+sudo -u git -H bundle exec rake gitlab:satellites:create RAILS_ENV=production
+
+# Clear redis cache
+sudo -u git -H bundle exec rake cache:clear RAILS_ENV=production
+
+# Clear and precompile assets
+sudo -u git -H bundle exec rake assets:clean RAILS_ENV=production
+sudo -u git -H bundle exec rake assets:precompile RAILS_ENV=production
+```
+
+### 6. Update config files
+
+Note: We switched from Puma in GitLab 5.x to unicorn in GitLab 6.0.
+
+* Make `/home/git/gitlab/config/gitlab.yml` the same as https://github.com/gitlabhq/gitlabhq/blob/master/config/gitlab.yml.example but with your settings.
+* Make `/home/git/gitlab/config/unicorn.rb` the same as https://github.com/gitlabhq/gitlabhq/blob/master/config/unicorn.rb.example but with your settings.
+
+### 7. Update Init script
+
+```bash
+cd /home/git/gitlab
+sudo rm /etc/init.d/gitlab
+sudo cp lib/support/init.d/gitlab /etc/init.d/gitlab 
+sudo chmod +x /etc/init.d/gitlab
+```
+
+### 8. Create uploads directory
+
+```bash
+cd /home/git/gitlab
+sudo -u git -H mkdir -p public/uploads
+sudo chmod -R u+rwX  public/uploads
+```
+
+### 9. Start application
+
+    sudo service gitlab start
+    sudo service nginx restart
+
+### 10. 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!
+
+## Things went south? Revert to previous version (5.1)
+
+### 1. Revert the code to the previous version
+Follow the [`upgrade guide from 5.0 to 5.1`](5.0-to-5.1.md), except for the database migration 
+(The backup is already migrated to the previous version)
+
+### 2. Restore from the backup:
+
+```bash
+cd /home/git/gitlab
+sudo -u git -H bundle exec rake gitlab:backup:restore RAILS_ENV=production
+```
+
+### Troubleshooting
+The migrations in this update are very sensitive to incomplete or inconsistent data. If you have a long-running GitLab installation and some of the previous upgrades did not work out 100% correct this may bite you now. The following commands can be run in the rails console to look for 'bad' data.
+
+All project owners should have an owner
+```
+Project.all.select { |project| project.owner.blank? }
+```
+
+Every user should have a namespace
+```
+User.all.select { |u| u.namespace.blank? }
+```
+
+Projects in the global namespace should not conflict with projects in the owner namespace
+```
+Project.where(namespace_id: nil).select { |p| Project.where(path: p.path, namespace_id: p.owner.try(:namespace).try(:id)).present? }
+```