Merge branch 'missing-upgrade-doc' into 'master'

add 7.9-7.10 upgrade doc

See merge request !560

7.9-to-7.10

+# From 7.9 to 7.10
+
+### 0. Stop server
+
+    sudo service gitlab stop
+
+### 1. Backup
+
+```bash
+cd /home/git/gitlab
+sudo -u git -H bundle exec rake gitlab:backup:create RAILS_ENV=production
+```
+
+### 2. Get latest code
+
+```bash
+sudo -u git -H git fetch --all
+sudo -u git -H git checkout -- db/schema.rb # local changes will be restored automatically
+```
+
+For GitLab Community Edition:
+
+```bash
+sudo -u git -H git checkout 7-10-stable
+```
+
+OR
+
+For GitLab Enterprise Edition:
+
+```bash
+sudo -u git -H git checkout 7-10-stable-ee
+```
+
+### 3. Update gitlab-shell
+
+```bash
+cd /home/git/gitlab-shell
+sudo -u git -H git fetch
+sudo -u git -H git checkout v2.6.2
+```
+
+### 4. 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
+
+# Clean up assets and cache
+sudo -u git -H bundle exec rake assets:clean assets:precompile cache:clear RAILS_ENV=production
+
+# Update init.d script
+sudo cp lib/support/init.d/gitlab /etc/init.d/gitlab
+```
+
+### 5. Update config files
+
+#### New configuration options for `gitlab.yml`
+
+There are new configuration options available for [`gitlab.yml`](config/gitlab.yml.example). View them with the command below and apply them to your current `gitlab.yml`.
+
+```
+git diff origin/7-9-stable:config/gitlab.yml.example origin/7-10-stable:config/gitlab.yml.example
+```
+
+#### Change Nginx settings
+
+* HTTP setups: Make `/etc/nginx/sites-available/gitlab` the same as [`lib/support/nginx/gitlab`](/lib/support/nginx/gitlab) but with your settings.
+* HTTPS setups: Make `/etc/nginx/sites-available/gitlab-ssl` the same as [`lib/support/nginx/gitlab-ssl`](/lib/support/nginx/gitlab-ssl) but with your settings.
+* A new `location /uploads/` section has been added that needs to have the same content as the existing `location @gitlab` section.
+
+#### Setup time zone (optional)
+
+Consider setting the time zone in `gitlab.yml` otherwise GitLab will default to UTC. If you set a time zone previously in [`application.rb`](config/application.rb) (unlikely), unset it.
+
+### 6. Start application
+
+    sudo service gitlab start
+    sudo service nginx restart
+
+### 7. 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 is complete!
+
+### 8. GitHub settings (if applicable)
+
+If you are using GitHub as an OAuth provider for authentication, you should change the callback URL so that it
+only contains a root URL (ex. `https://gitlab.example.com/`)
+
+## Things went south? Revert to previous version (7.9)
+
+### 1. Revert the code to the previous version
+Follow the [upgrade guide from 7.8 to 7.8](7.8-to-7.9.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
+```
+If you have more than one backup *.tar file(s) please add `BACKUP=timestamp_of_backup` to the command above.
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