Fix #4131: Upgrade to Ruby 2.6.

Upgrade procedure:

    $ echo 2.6.3 > .ruby-version

    # upgrade ruby-build to know about the latest ruby versions.
    # see also: github.com/rkh/rbenv-update
    $ cd ~/.rbenv/plugins/ruby-build && git pull

    # install the version of ruby specified in .ruby-version.
    # see also: github.com/capistrano/rbenv/issues/83
    $ rbenv install --skip-existing

    # update the shell to use the latest version of ruby by default.
    $ rbenv global 2.6.3

    # update rubygems and bundler
    $ gem update --system

    # update the lockfile to use the latest version of bundler
    $ bundle update --bundler

.ruby-version

@@ -1 +1 @@
-2.5.1
+2.6.3

Gemfile.lock

@@ -521,4 +521,4 @@ DEPENDENCIES
   whenever
 
 BUNDLED WITH
-   1.16.1
+   2.0.2

INSTALL.debian

@@ -2,7 +2,7 @@
 
 # Run: curl -L -s https://raw.githubusercontent.com/r888888888/danbooru/master/INSTALL.debian -o install.sh ; chmod +x install.sh ; ./install.sh
 
-export RUBY_VERSION=2.5.1
+export RUBY_VERSION=2.6.3
 export GITHUB_INSTALL_SCRIPTS=https://raw.githubusercontent.com/r888888888/danbooru/master/script/install
 export VIPS_VERSION=8.7.0
 

config/deploy.rb

@@ -3,7 +3,6 @@ set :default_stage, "staging"
 set :application, "danbooru"
 set :repo_url,  "git://github.com/r888888888/danbooru.git"
 set :deploy_to, "/var/www/danbooru2"
-set :rbenv_ruby, "2.5.1"
 append :linked_dirs, "log", "tmp/pids", "tmp/cache", "tmp/sockets", "vendor/bundle"
 set :branch, ENV.fetch("branch", "master")
 

config/deploy/production.rb

@@ -1,6 +1,5 @@
 set :user, "danbooru"
 set :rails_env, "production"
-set :rbenv_path, "/home/danbooru/.rbenv"
 append :linked_files, ".env.production"
 
 server "kagamihara", :roles => %w(web app), :primary => true

config/deploy/staging.rb

@@ -3,5 +3,4 @@ set :rails_env, "staging"
 server "testbooru.donmai.us", :roles => %w(web app db), :primary => true, :user => "danbooru"
 
 set :linked_files, fetch(:linked_files, []).push(".env.staging")
-set :rbenv_path, "/home/danbooru/.rbenv"
 set :deploy_to, "/var/www/danbooru2"

config/docker/danbooru-base

@@ -1,4 +1,4 @@
-FROM ruby:2.5.1-slim-stretch
+FROM ruby:2.6.3-slim-stretch
 
 ENV DOCKERIZE_VERSION v0.6.1
 ENV VIPS_VERSION 8.7.0

script/install/app_server.sh

@@ -5,7 +5,7 @@
 #
 # Run: curl -L -s https://raw.githubusercontent.com/r888888888/danbooru/master/script/install/app_server.sh | sh
 
-export RUBY_VERSION=2.5.1
+export RUBY_VERSION=2.6.3
 export GITHUB_INSTALL_SCRIPTS=https://raw.githubusercontent.com/r888888888/danbooru/master/script/install
 export VIPS_VERSION=8.7.0