Merge branch 'ruby-2-3-lets-not-break-things' into 'master'

Use Ruby 2.3.1

## What does this MR do?

This WIP MR will eventually introduce 2.3 as default language for GitLab CE/EE

## Why was this MR needed?

@connorshea wants to be prepared for Rails 5.0, so we need Ruby > 2.2, so why not go 2.3 already?

## What are the relevant issue numbers?

Closes #12507 

## TODO

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] All builds are passing
- [ ] [Omnibus uses 2.3.1](https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/847)

See merge request !4948

.gitlab-ci.yml

-image: "ruby:2.1"
+image: "ruby:2.3"
 
 cache:
-  key: "ruby21"
+  key: "ruby-23"
   paths:
   - vendor/apt
   - vendor/ruby
@@ -138,57 +138,57 @@ spinach 7 10: *spinach-knapsack
 spinach 8 10: *spinach-knapsack
 spinach 9 10: *spinach-knapsack
 
-# Execute all testing suites against Ruby 2.3
-.ruby-23: &ruby-23
-  image: "ruby:2.3"
+# Execute all testing suites against Ruby 2.1
+.ruby-21: &ruby-21
+  image: "ruby:2.1"
   <<: *use-db
   only:
     - master
   cache:
-    key: "ruby-23"
+    key: "ruby21"
     paths:
       - vendor/apt
       - vendor/ruby
 
-.rspec-knapsack-ruby23: &rspec-knapsack-ruby23
+.rspec-knapsack-ruby21: &rspec-knapsack-ruby21
   <<: *rspec-knapsack
-  <<: *ruby-23
+  <<: *ruby-21
 
-.spinach-knapsack-ruby23: &spinach-knapsack-ruby23
+.spinach-knapsack-ruby21: &spinach-knapsack-ruby21
   <<: *spinach-knapsack
-  <<: *ruby-23
+  <<: *ruby-21
 
-rspec 0 20 ruby23: *rspec-knapsack-ruby23
-rspec 1 20 ruby23: *rspec-knapsack-ruby23
-rspec 2 20 ruby23: *rspec-knapsack-ruby23
-rspec 3 20 ruby23: *rspec-knapsack-ruby23
-rspec 4 20 ruby23: *rspec-knapsack-ruby23
-rspec 5 20 ruby23: *rspec-knapsack-ruby23
-rspec 6 20 ruby23: *rspec-knapsack-ruby23
-rspec 7 20 ruby23: *rspec-knapsack-ruby23
-rspec 8 20 ruby23: *rspec-knapsack-ruby23
-rspec 9 20 ruby23: *rspec-knapsack-ruby23
-rspec 10 20 ruby23: *rspec-knapsack-ruby23
-rspec 11 20 ruby23: *rspec-knapsack-ruby23
-rspec 12 20 ruby23: *rspec-knapsack-ruby23
-rspec 13 20 ruby23: *rspec-knapsack-ruby23
-rspec 14 20 ruby23: *rspec-knapsack-ruby23
-rspec 15 20 ruby23: *rspec-knapsack-ruby23
-rspec 16 20 ruby23: *rspec-knapsack-ruby23
-rspec 17 20 ruby23: *rspec-knapsack-ruby23
-rspec 18 20 ruby23: *rspec-knapsack-ruby23
-rspec 19 20 ruby23: *rspec-knapsack-ruby23
+rspec 0 20 ruby21: *rspec-knapsack-ruby21
+rspec 1 20 ruby21: *rspec-knapsack-ruby21
+rspec 2 20 ruby21: *rspec-knapsack-ruby21
+rspec 3 20 ruby21: *rspec-knapsack-ruby21
+rspec 4 20 ruby21: *rspec-knapsack-ruby21
+rspec 5 20 ruby21: *rspec-knapsack-ruby21
+rspec 6 20 ruby21: *rspec-knapsack-ruby21
+rspec 7 20 ruby21: *rspec-knapsack-ruby21
+rspec 8 20 ruby21: *rspec-knapsack-ruby21
+rspec 9 20 ruby21: *rspec-knapsack-ruby21
+rspec 10 20 ruby21: *rspec-knapsack-ruby21
+rspec 11 20 ruby21: *rspec-knapsack-ruby21
+rspec 12 20 ruby21: *rspec-knapsack-ruby21
+rspec 13 20 ruby21: *rspec-knapsack-ruby21
+rspec 14 20 ruby21: *rspec-knapsack-ruby21
+rspec 15 20 ruby21: *rspec-knapsack-ruby21
+rspec 16 20 ruby21: *rspec-knapsack-ruby21
+rspec 17 20 ruby21: *rspec-knapsack-ruby21
+rspec 18 20 ruby21: *rspec-knapsack-ruby21
+rspec 19 20 ruby21: *rspec-knapsack-ruby21
 
-spinach 0 10 ruby23: *spinach-knapsack-ruby23
-spinach 1 10 ruby23: *spinach-knapsack-ruby23
-spinach 2 10 ruby23: *spinach-knapsack-ruby23
-spinach 3 10 ruby23: *spinach-knapsack-ruby23
-spinach 4 10 ruby23: *spinach-knapsack-ruby23
-spinach 5 10 ruby23: *spinach-knapsack-ruby23
-spinach 6 10 ruby23: *spinach-knapsack-ruby23
-spinach 7 10 ruby23: *spinach-knapsack-ruby23
-spinach 8 10 ruby23: *spinach-knapsack-ruby23
-spinach 9 10 ruby23: *spinach-knapsack-ruby23
+spinach 0 10 ruby21: *spinach-knapsack-ruby21
+spinach 1 10 ruby21: *spinach-knapsack-ruby21
+spinach 2 10 ruby21: *spinach-knapsack-ruby21
+spinach 3 10 ruby21: *spinach-knapsack-ruby21
+spinach 4 10 ruby21: *spinach-knapsack-ruby21
+spinach 5 10 ruby21: *spinach-knapsack-ruby21
+spinach 6 10 ruby21: *spinach-knapsack-ruby21
+spinach 7 10 ruby21: *spinach-knapsack-ruby21
+spinach 8 10 ruby21: *spinach-knapsack-ruby21
+spinach 9 10 ruby21: *spinach-knapsack-ruby21
 
 # Other generic tests
 

.ruby-version

-2.1.8
+2.3.1

CHANGELOG

@@ -6,6 +6,7 @@ v 8.11.0 (unreleased)
   - Fix rename `add_users_into_project` and `projects_ids`. !20512 (herminiotorres)
   - Fix the title of the toggle dropdown button. !5515 (herminiotorres)
   - Rename `markdown_preview` routes to `preview_markdown`. (Christopher Bartz)
+  - Update to Ruby 2.3.1. !4948
   - Improve diff performance by eliminating redundant checks for text blobs
   - Ensure that branch names containing escapable characters (e.g. %20) aren't unescaped indiscriminately. !5770 (ewiltshi)
   - Convert switch icon into icon font (ClemMakesApps)

doc/install/installation.md

@@ -108,8 +108,7 @@ Then select 'Internet Site' and press enter to confirm the hostname.
 
 ## 2. Ruby
 
-_**Note:** The current supported Ruby version is 2.1.x. Ruby 2.2 and 2.3 are
-currently not supported._
+_**Note:** The current supported Ruby versions are 2.1.x and 2.3.x. 2.3.x is preferred, and support for 2.1.x will be dropped in the future.
 
 The use of Ruby version managers such as [RVM], [rbenv] or [chruby] with GitLab
 in production, frequently leads to hard to diagnose problems. For example,
@@ -124,9 +123,9 @@ Remove the old Ruby 1.8 if present:
 Download Ruby and compile it:
 
     mkdir /tmp/ruby && cd /tmp/ruby
-    curl --remote-name --progress https://cache.ruby-lang.org/pub/ruby/2.1/ruby-2.1.8.tar.gz
-    echo 'c7e50159357afd87b13dc5eaf4ac486a70011149  ruby-2.1.8.tar.gz' | shasum -c - && tar xzf ruby-2.1.8.tar.gz
-    cd ruby-2.1.8
+    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 -c - && tar xzf ruby-2.3.1.tar.gz
+    cd ruby-2.3.1
     ./configure --disable-install-rdoc
     make
     sudo make install
@@ -591,13 +590,13 @@ for the changes to take effect.
 If you'd like to connect to a Redis server on a non-standard port or on a different host, you can configure its connection string via the `config/resque.yml` file.
 
     # example
-    production: 
+    production:
       url: redis://redis.example.tld:6379
 
 If you want to connect the Redis server via socket, then use the "unix:" URL scheme and the path to the Redis socket file in the `config/resque.yml` file.
 
     # example
-    production: 
+    production:
       url: unix:/path/to/redis/socket
 
 ### Custom SSH Connection