Add Rails 5.2 and 6.0 to build, fixing up issues

In addition to adding scenarios for 5.2 and 6.0, I had to do some
cleanup to get everything working well:

* Replace string-based version checks with numeric ones, and update all
  version checks to treat 6+ the same as 5 (except where necessary).

* Avoid touching `ActiveSupport::Deprecation::DeprecationProxy`
  instances to fix a couple of warnings in Rails 6.

* Update Bundler as part of container setup, because Rails 6's config
  seems to rely on a newer version of Bundler than the one that comes
  with the Ruby image.

* Update the regexes in the `show-routes` spec to be compatible with 5.2
  and up.

* Add a new code path to `show-routes` for Rails 6.

* Upgrade all bundles, just for hygiene.

scenarios/rails30.dockerfile

@@ -2,4 +2,4 @@ FROM ruby:2.0
 RUN mkdir -p /scenario
 WORKDIR /scenario
 ENV LANG=C.UTF-8
-CMD (bundle check || bundle install) && bundle exec rake
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails31.dockerfile

@@ -2,4 +2,4 @@ FROM ruby:2.0
 RUN mkdir -p /scenario
 WORKDIR /scenario
 ENV LANG=C.UTF-8
-CMD (bundle check || bundle install) && bundle exec rake
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails32.dockerfile

@@ -2,4 +2,4 @@ FROM ruby:2.0
 RUN mkdir -p /scenario
 WORKDIR /scenario
 ENV LANG=C.UTF-8
-CMD (bundle check || bundle install) && bundle exec rake
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails40.dockerfile

@@ -2,4 +2,4 @@ FROM ruby:2.3
 RUN mkdir -p /scenario
 WORKDIR /scenario
 ENV LANG=C.UTF-8
-CMD (bundle check || bundle install) && bundle exec rake
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails41.dockerfile

@@ -2,4 +2,4 @@ FROM ruby:2.3
 RUN mkdir -p /scenario
 WORKDIR /scenario
 ENV LANG=C.UTF-8
-CMD (bundle check || bundle install) && bundle exec rake
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails42.dockerfile

@@ -2,4 +2,4 @@ FROM ruby:2.4
 RUN mkdir -p /scenario
 WORKDIR /scenario
 ENV LANG=C.UTF-8
-CMD (bundle check || bundle install) && bundle exec rake
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails50.dockerfile

@@ -2,4 +2,4 @@ FROM ruby:2.4
 RUN mkdir -p /scenario
 WORKDIR /scenario
 ENV LANG=C.UTF-8
-CMD (bundle check || bundle install) && bundle exec rake
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails51.dockerfile

@@ -2,4 +2,4 @@ FROM ruby:2.4
 RUN mkdir -p /scenario
 WORKDIR /scenario
 ENV LANG=C.UTF-8
-CMD (bundle check || bundle install) && bundle exec rake
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails52.docker-compose.yml

@@ -0,0 +1,15 @@
+---
+version: "2"
+services:
+  scenario:
+    build:
+      context: ..
+      dockerfile: scenarios/rails52.dockerfile
+    image: pryrails_scenario_rails52
+    volumes:
+    - "..:/scenario"
+    - "bundle_rails52:/usr/local/bundle"
+    environment:
+      BUNDLE_GEMFILE: scenarios/rails52.gemfile
+volumes:
+  bundle_rails52: {}

scenarios/rails52.dockerfile

@@ -0,0 +1,5 @@
+FROM ruby:2.4
+RUN mkdir -p /scenario
+WORKDIR /scenario
+ENV LANG=C.UTF-8
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails52.gemfile

@@ -0,0 +1,7 @@
+source "https://rubygems.org"
+
+gem "rails", "~> 5.2.0"
+gem "mongoid"
+gem "sqlite3"
+
+gemspec :path => "../"

scenarios/rails60.docker-compose.yml

@@ -0,0 +1,15 @@
+---
+version: "2"
+services:
+  scenario:
+    build:
+      context: ..
+      dockerfile: scenarios/rails60.dockerfile
+    image: pryrails_scenario_rails60
+    volumes:
+    - "..:/scenario"
+    - "bundle_rails60:/usr/local/bundle"
+    environment:
+      BUNDLE_GEMFILE: scenarios/rails60.gemfile
+volumes:
+  bundle_rails60: {}

scenarios/rails60.dockerfile

@@ -0,0 +1,5 @@
+FROM ruby:2.5
+RUN mkdir -p /scenario
+WORKDIR /scenario
+ENV LANG=C.UTF-8
+CMD (bundle check || (gem install bundler && bundle install)) && bundle exec rake

scenarios/rails60.gemfile

@@ -0,0 +1,7 @@
+source "https://rubygems.org"
+
+gem "rails", github: "rails/rails"
+gem "mongoid"
+gem "sqlite3"
+
+gemspec :path => "../"