Add 8.0-to-8.1 update guide

doc/update/8.0-to-8.1.md

+# From 8.0 to 8.1
+
+### 0. Double-check your Git version
+
+**This notice applies only to /usr/local/bin/git**
+
+If you compiled Git from source on your GitLab server then please double-check
+that you are using a version that protects against CVE-2014-9390. For six
+months after this vulnerability became known the GitLab installation guide
+still contained instructions that would install the outdated, 'vulnerable' Git
+version 2.1.2.
+
+Run the following command to get your current Git version:
+
+```sh
+/usr/local/bin/git --version
+```
+
+If you see 'No such file or directory' then you did not install Git according
+to the outdated instructions from the GitLab installation guide and you can go
+to the next step 'Stop server' below.
+
+If you see a version string then it should be v1.8.5.6, v1.9.5, v2.0.5, v2.1.4,
+v2.2.1 or newer. You can use the [instructions in the GitLab source
+installation
+guide](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/install/installation.md#1-packages-dependencies)
+to install a newer version of Git.
+
+### 1. Stop server
+
+    sudo service gitlab stop
+
+### 2. Backup
+
+```bash
+cd /home/git/gitlab
+sudo -u git -H bundle exec rake gitlab:backup:create RAILS_ENV=production
+```
+
+### 3. 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 8-1-stable
+```
+
+OR
+
+For GitLab Enterprise Edition:
+
+```bash
+sudo -u git -H git checkout 8-1-stable-ee
+```
+
+### 4. Update gitlab-shell
+
+```bash
+cd /home/git/gitlab-shell
+sudo -u git -H git fetch
+sudo -u git -H git checkout v2.6.5
+```
+
+### 5. Install gitlab-git-http-server
+
+First we download Go 1.5 and install it into `/usr/local/go`:
+
+```bash
+curl -O --progress https://storage.googleapis.com/golang/go1.5.linux-amd64.tar.gz
+echo '5817fa4b2252afdb02e11e8b9dc1d9173ef3bd5a  go1.5.linux-amd64.tar.gz' | shasum -c - && \
+  sudo tar -C /usr/local -xzf go1.5.linux-amd64.tar.gz
+sudo ln -sf /usr/local/go/bin/{go,godoc,gofmt} /usr/local/bin/
+rm go1.5.linux-amd64.tar.gz
+```
+
+Now we download `gitlab-git-http-server` and install it in `/home/git/gitlab-git-http-server`:
+
+```bash
+cd /home/git
+sudo -u git -H git clone https://gitlab.com/gitlab-org/gitlab-git-http-server.git
+cd gitlab-git-http-server
+sudo -u git -H make
+```
+
+Make sure your unicorn.rb file contains a 'listen' line for
+'127.0.0.1:8080' and that this line is not commented out.
+
+```
+cd /home/git/gitlab
+grep ^listen config/unicorn.rb
+
+# If there is no 'listen' line for 127.0.0.1:8080, add it:
+sudo -u git tee -a config/unicorn.rb <<EOF
+listen "127.0.0.1:8080", :tcp_nopush => true
+EOF
+```
+
+If your Git repositories are in a directory other than `/home/git/repositories`,
+you need to tell `gitlab-git-http-server` about it via `/etc/default/gitlab`.
+See `lib/support/init.d/gitlab.default.example` for the options.
+
+### 6. Copy secrets
+
+The `secrets.yml` file is used to store keys to encrypt sessions and encrypt secure variables.
+When you run migrations make sure to store it someplace safe.
+Don't store it in the same place as your database backups,
+otherwise your secrets are exposed if one of your backups is compromised.
+
+```
+cd /home/git/gitlab
+sudo -u git -H cp config/secrets.yml.example config/secrets.yml
+sudo -u git -H chmod 0600 config/secrets.yml
+```
+
+### 7. 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 postgres development test --deployment
+
+# PostgreSQL installations (note: the line below states '--without mysql')
+sudo -u git -H bundle install --without mysql development test --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
+```
+
+### 8. 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 manually to your current `gitlab.yml`:
+
+```sh
+git diff origin/8-0-stable:config/gitlab.yml.example origin/8-1-stable:config/gitlab.yml.example
+```
+
+The new options include configuration of GitLab CI that are now being part of GitLab CE and EE.
+
+#### New Nginx configuration
+
+Because of the new `gitlab-git-http-server` you need to update your Nginx
+configuration.  If you skip this step 'git clone' and 'git push' over HTTP(S)
+will stop working.
+
+View changes between the previous recommended Nginx configuration and the
+current one:
+
+```sh
+# For HTTPS configurations
+git diff origin/8-0-stable:lib/support/nginx/gitlab-ssl origin/8-1-stable:lib/support/nginx/gitlab-ssl
+
+# For HTTP configurations
+git diff origin/8-0-stable:lib/support/nginx/gitlab origin/8-1-stable:lib/support/nginx/gitlab
+```
+
+If you are using Apache instead of NGINX please see the updated [Apache templates](https://gitlab.com/gitlab-org/gitlab-recipes/tree/master/web-server/apache).
+Also note that because Apache does not support upstreams behind Unix sockets you will need to let gitlab-git-http-server listen on a TCP port. You can do this via [/etc/default/gitlab](https://gitlab.com/gitlab-org/gitlab-ce/blob/8-0-stable/lib/support/init.d/gitlab.default.example#L34).
+
+### 9. Migrate GitLab CI to GitLab CE/EE
+
+Now, GitLab CE and EE has CI integrated. However, migrations don't happen automatically and you need to do it manually.
+Please follow the following guide [to migrate](../migrate_ci_to_ce/README.md) your GitLab CI instance to GitLab CE/EE.
+
+### 10. Use Redis v2.4.0+
+
+Previous versions of GitLab allowed Redis versions >= 2.0 to be used, but
+Sidekiq jobs could fail due to lack of support for the SREM command. GitLab
+8.0 now checks that Redis >= 2.4.0 is used. You can check your Redis version
+with the following command:
+
+    redis-cli info | grep redis_version
+
+### 11. Start application
+
+    sudo service gitlab start
+    sudo service nginx restart
+
+### 12. 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:
+
+    sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production
+
+If all items are green, then congratulations, the upgrade is complete!
+
+## Things went south? Revert to previous version (8.0)
+
+### 1. Revert the code to the previous version
+
+Follow the [upgrade guide from 7.14 to 8.0](7.14-to-8.0.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
+```
+
+If you have more than one backup `*.tar` file(s) please add `BACKUP=timestamp_of_backup` to the command above.
+
+## Troubleshooting
+
+### "You appear to have cloned an empty repository."
+
+If you see this message when attempting to clone a repository hosted by GitLab,
+this is likely due to an outdated Nginx or Apache configuration, or a missing or
+misconfigured `gitlab-git-http-server` instance. Double-check that you correctly
+completed [Step 5](#5-install-gitlab-git-http-server) to install the daemon and
+[Step 8](#new-nginx-configuration) to reconfigure Nginx.