Add a script for using dev containers outside VSCode

I want to use the devcontainer info, but I don't want to use VSCode.
This commit adds a small script that reads the devcontainer JSON file
and runs docker commands based on the information in the JSON file.

Usage is like this:

In terminal 1, run `tool/devcontainer up`

After that thing is running do `tool/devcontainer run-user-commands` to
make sure gems are bundled and database is set up.

Finally run `tool/devcontainer sh` to get a shell inside the container.

Author: tenderlove

.devcontainer/boot.sh

@@ -1,7 +1,9 @@
 bundle install
 
-. ${NVM_DIR}/nvm.sh && nvm install --lts
-yarn install
+if [[ ! -z "${NVM_DIR}" ]]; then
+  . ${NVM_DIR}/nvm.sh && nvm install --lts
+  yarn install
+fi
 
 cd activerecord
 

.devcontainer/devcontainer.json

@@ -39,7 +39,7 @@
 				"Shopify.ruby-lsp"
 			]
 		}
-	},
+	}
 
 	// Uncomment to connect as root instead. More info: https://containers.dev/implementors/json_reference/#remoteUser.
 	// "remoteUser": "root"

tools/devcontainer

@@ -0,0 +1,30 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "json"
+require "open3"
+
+VARS = {
+  "localWorkspaceFolderBasename" => Dir.pwd.split(File::SEPARATOR).last
+}
+
+data = File.binread ".devcontainer/devcontainer.json"
+data.gsub!(/^\s*\/\/.*$/, "") # strip comments
+info = JSON.load data
+
+working_dir = info["workspaceFolder"].gsub(/\${([^}]*)}/) { |x|
+  VARS.fetch($1)
+}
+
+env = info["containerEnv"].map { |k, v| "-e #{k}=#{v}" }.join " "
+
+case ARGV[0]
+when "up"
+  system "docker compose -f .devcontainer/#{info["dockerComposeFile"]} up"
+when "run-user-commands"
+  service_id, _, _ = Open3.capture3("docker ps -q -f name=#{info["service"]}")
+  system "docker exec #{env} -w #{working_dir} -it #{service_id.chomp} /bin/bash -i #{info["postCreateCommand"]}"
+when "sh"
+  service_id, _, _ = Open3.capture3("docker ps -q -f name=#{info["service"]}")
+  system "docker exec #{env} -w #{working_dir} -it #{service_id.chomp} /bin/bash"
+end