Merge branch 'cs-upgrade-ruby-docs' into 'master'

Add Ruby 2.3 upgrade notes.

The 8.10 to 8.11 docs didn't mention Ruby 2.3, now they do.

See merge request !5940

doc/update/8.10-to-8.11.md

@@ -20,7 +20,31 @@ cd /home/git/gitlab
 sudo -u git -H bundle exec rake gitlab:backup:create RAILS_ENV=production
 ```
 
-### 3. Get latest code
+### 3. Update Ruby
+
+If you are you running Ruby 2.1.x, you do not _need_ to upgrade Ruby yet, but you should note that support for 2.1.x is deprecated and we will require 2.3.x in 8.13. It's strongly recommended that you upgrade as soon as possible.
+
+You can check which version you are running with `ruby -v`.
+
+Download and compile Ruby:
+
+``bash
+mkdir /tmp/ruby && cd /tmp/ruby
+curl --remote-name --progress https://cache.ruby-lang.org/pub/ruby/2.3/ruby-2.3.1.tar.gz
+echo 'c39b4001f7acb4e334cb60a0f4df72d434bef711  ruby-2.3.1.tar.gz' | shasum --check - && tar xzf ruby-2.3.1.tar.gz
+cd ruby-2.3.1
+./configure --disable-install-rdoc
+make
+sudo make install
+``
+
+Install Bundler:
+
+``bash
+sudo gem install bundler --no-ri --no-rdoc
+``
+
+### 4. Get latest code
 
 ```bash
 sudo -u git -H git fetch --all
@@ -41,7 +65,7 @@ For GitLab Enterprise Edition:
 sudo -u git -H git checkout 8-11-stable-ee
 ```
 
-### 4. Update gitlab-shell
+### 5. Update gitlab-shell
 
 ```bash
 cd /home/git/gitlab-shell
@@ -49,7 +73,7 @@ sudo -u git -H git fetch --all --tags
 sudo -u git -H git checkout v3.4.0
 ```
 
-### 5. Update gitlab-workhorse
+### 6. Update gitlab-workhorse
 
 Install and compile gitlab-workhorse. This requires
 [Go 1.5](https://golang.org/dl) which should already be on your system from
@@ -62,7 +86,7 @@ sudo -u git -H git checkout v0.7.8
 sudo -u git -H make
 ```
 
-### 6. Install libs, migrations, etc.
+### 7. Install libs, migrations, etc.
 
 ```bash
 cd /home/git/gitlab
@@ -84,7 +108,7 @@ sudo -u git -H bundle exec rake assets:clean assets:precompile cache:clear RAILS
 
 ```
 
-### 7. Update configuration files
+### 8. Update configuration files
 
 #### New configuration options for `gitlab.yml`
 
@@ -133,12 +157,12 @@ Ensure you're still up-to-date with the latest init script changes:
 
     sudo cp lib/support/init.d/gitlab /etc/init.d/gitlab
 
-### 8. Start application
+### 9. Start application
 
     sudo service gitlab start
     sudo service nginx restart
 
-### 9. Check application status
+### 10. Check application status
 
 Check if GitLab and its environment are configured correctly: