Add 6.0-to-7.2.md guide ahead of 7.2 release

doc/update/6.0-to-7.2.md

+# From 6.0 to 7.2
+
+# GitLab 7.2 has not been released yet!
+
+## Global issue numbers
+
+As of 6.1 issue numbers are project specific. This means all issues are renumbered and get a new number in their URL. If you use an old issue number URL and the issue number does not exist yet you are redirected to the new one. This conversion does not trigger if the old number already exists for this project, this is unlikely but will happen with old issues and large projects.
+
+## 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 --all
+```
+
+For GitLab Community Edition:
+
+```bash
+sudo -u git -H git checkout 7-2-stable
+```
+
+OR
+
+For GitLab Enterprise Edition:
+
+```bash
+sudo -u git -H git checkout 7-2-stable-ee
+```
+
+
+## 3. Install additional packages
+
+```bash
+# Add support for lograte for better log file handling
+sudo apt-get install logrotate
+```
+
+## 4. Update gitlab-shell
+
+```bash
+cd /home/git/gitlab-shell
+sudo -u git -H git fetch
+sudo -u git -H git checkout v1.9.7
+```
+
+## 5. Install libs, migrations, etc.
+
+```bash
+cd /home/git/gitlab
+
+# MySQL installations (note: the line below states '--without ... postgres')
+sudo -u git -H bundle install --without development test postgres --deployment
+
+# PostgreSQL installations (note: the line below states '--without ... mysql')
+sudo -u git -H bundle install --without development test mysql --deployment
+
+
+# Run database migrations
+sudo -u git -H bundle exec rake db:migrate RAILS_ENV=production
+
+# Enable internal issue IDs (introduced in GitLab 6.1)
+sudo -u git -H bundle exec rake migrate_iids RAILS_ENV=production
+
+# Clean up assets and cache
+sudo -u git -H bundle exec rake assets:clean assets:precompile cache:clear RAILS_ENV=production
+
+# Close access to gitlab-satellites for others
+sudo chmod u+rwx,g+rx,o-rwx /home/git/gitlab-satellites
+```
+
+## 6. Update config files
+
+TIP: to see what changed in gitlab.yml.example in this release use next command: 
+
+```
+git diff 6-0-stable:config/gitlab.yml.example 7-2-stable:config/gitlab.yml.example
+```
+
+* Make `/home/git/gitlab/config/gitlab.yml` the same as https://gitlab.com/gitlab-org/gitlab-ce/blob/7-2-stable/config/gitlab.yml.example but with your settings.
+* Make `/home/git/gitlab/config/unicorn.rb` the same as https://gitlab.com/gitlab-org/gitlab-ce/blob/7-2-stable/config/unicorn.rb.example but with your settings.
+* Make `/etc/nginx/sites-available/nginx` the same as https://gitlab.com/gitlab-org/gitlab-ce/blob/7-2-stable/lib/support/nginx/gitlab but with your settings.
+* Copy rack attack middleware config
+
+```bash
+sudo -u git -H cp config/initializers/rack_attack.rb.example config/initializers/rack_attack.rb
+```
+
+* Set up logrotate
+
+```bash
+sudo cp lib/support/logrotate/gitlab /etc/logrotate.d/gitlab
+```
+
+## 7. Update Init script
+
+```bash
+sudo cp lib/support/init.d/gitlab /etc/init.d/gitlab
+```
+
+## 8. Start application
+
+    sudo service gitlab start
+    sudo service nginx restart
+
+## 9. Check application status
+
+Check if GitLab and its environment are configured correctly:
+
+    cd /home/git/gitlab
+    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 (6.0)
+
+### 1. Revert the code to the previous version
+
+Follow the [`upgrade guide from 5.4 to 6.0`](5.4-to-6.0.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
+```
+
+## Login issues after upgrade?
+
+If running in HTTPS mode, be sure to read [Can't Verify CSRF token authenticity](https://github.com/gitlabhq/gitlab-public-wiki/wiki/Trouble-Shooting-Guide#cant-verify-csrf-token-authenticitycant-get-past-login-pageredirected-to-login-page)