Rakeify docker compose generator

docker-compose.yml

@@ -1,5 +1,5 @@
 # Please do NOT manually edit this file.
-# This file is generated by 'bin/generate_docker_compose.rb'
+# This file is generated by 'bundle exec rake docker:compose:generate'
 ---
 services:
   ruby-2.5:

tasks/docker/compose.rake

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+# @type self: Rake::DSL
+
+namespace :docker do
+  namespace :compose do
+    desc "Generate docker-compose.yml"
+    task :generate do
+      require "psych"
+      require "open3"
+
+      ruby_versions = [2.5, 2.6, 2.7, 3.0, 3.1, 3.2, 3.3]
+
+      services = ruby_versions.reduce({}) do |hash, version|
+        hash.merge(
+          "ruby-#{version}" => {
+            "build" => {
+              "context" => ".",
+              "dockerfile" => "images/ruby-#{version}.dockerfile"
+            },
+            "command" => "/bin/bash",
+            "environment" => {
+              "BUNDLE_GEMFILE" => "gemfiles/ruby-#{version}.gemfile"
+            },
+            "stdin_open" => true,
+            "tty" => true,
+            "volumes" => [
+              ".:/app",
+              "bundle-#{version}:/usr/local/bundle"
+            ]
+          }
+        )
+      end
+
+      volumes = ruby_versions.reduce({}) do |hash, version|
+        hash.merge("bundle-#{version}" => nil)
+      end
+
+      docker_compose = {
+        "services" => services,
+        "volumes" => volumes
+      }
+
+      target = "docker-compose.yml"
+
+      File.open(target, "w") do |f|
+        f.write("# Please do NOT manually edit this file.\n")
+        f.write("# This file is generated by 'rake docker:compose:generate'\n")
+        f.write(Psych.dump(docker_compose))
+      end
+
+      git_diff, _ = Open3.capture2("git diff --color #{target}")
+
+      if git_diff.empty?
+        puts "No changes. '#{target}' is up-to-date."
+      else
+        puts "'#{target}' has been updated. Please review the changes below:\n\n"
+        puts git_diff
+      end
+    end
+  end
+end