Add docker.rb to manage builds

Author: JaciBrunning

Dockerfile

@@ -2,9 +2,12 @@ FROM jaci/rails-base:5.2.3-alpine
 
 RUN apk add --no-cache sqlite-dev
 
-# Bundle install Gemfile first to take advantage of caching
-COPY ./Gemfile /app/Gemfile
-COPY ./Gemfile.lock /app/Gemfile.lock
+# Copy all dependency files over before the main stuff
+# The reason for this is that it reduces the number of layers that
+# require rebuilding. If we copied all the files here, the bundle install
+# layer would require rebuilding every time, which is both time and space
+# expensive.
+COPY ./build/depslayer /app
 
 RUN bundle install
 

docker.rb

@@ -0,0 +1,46 @@
+require 'fileutils'
+
+DOCKER_TAG=ENV.fetch('DOCKER_TAG') {"#{`git rev-parse --short HEAD`.strip}#{`git diff HEAD --quiet || echo -dirty`.strip}"}
+DOCKER_REPO=ENV.fetch('DOCKER_REPO') {"gcr.io/imjacinta/jaci/curtincourses"}
+
+DOCKER_IMG="#{DOCKER_REPO}:#{DOCKER_TAG}"
+
+def copy_deps
+  FileUtils.mkdir_p 'build/depslayer'
+  Dir.glob(['**/Gemfile', '**/Gemfile.lock', '**/*.gemspec']).each do |file|
+    next if file.include?('build/depslayer')
+    
+    dest = "build/depslayer/#{file}"
+    FileUtils.mkdir_p(File.dirname(dest))
+    
+    if !File.exist?(dest) || File.read(file) != File.read(dest)
+      puts "Update: #{file} -> #{dest}"
+      FileUtils.cp(file, dest) 
+    end
+  end
+end
+
+def docker_build
+  copy_deps
+  system "docker build -t #{DOCKER_IMG} ."
+end
+
+def docker_push
+  docker_build
+  system "docker push #{DOCKER_IMG}"
+end
+
+if __FILE__ == $0
+  act = ARGV[0]
+  if act == 'build'
+    docker_build
+  elsif act == 'push'
+    docker_push
+  elsif act == 'get_tag'
+    puts DOCKER_TAG
+  elsif act == 'get_img'
+    puts DOCKER_IMG
+  elsif act == 'get_repo'
+    puts DOCKER_REPO
+  end
+end