Support ask

As an alternative to `set`, `ask` takes a key and a default value. When
the key is called with `fetch` the user will be prompted to set the
value.

README.md

@@ -21,8 +21,9 @@ TODO:
 
   - [x] support set/fetch/role configuration
   - [x] basic deploy
+  - [x] ask
   - [ ] support existing significant configuration variables
-  - [ ] ask
+  - [ ] prefer `roles(:all)` over `all_roles`
   - [ ] support primary servers `on primary(:db)`
   - [ ] basic rollback
   - [ ] add examples to README
@@ -66,12 +67,13 @@ To create different stages:
 ## Configuration
 
     # config/deploy.rb
-
     set :application, 'example app'
 
     # config/deploy/production.rb
-
     set :stage, :production
+
+    ask :branch, :master
+
     role :app, %w{example.com}
     role :web, %w{example.com}
     role :db, %w{example.com}

lib/capistrano/configuration.rb

@@ -7,15 +7,21 @@ module Capistrano
       end
     end
 
+    def ask(key, default=nil)
+      question = Question.new(self, key, default)
+      set(key, question)
+    end
+
     def set(key, value)
       config[key] = value
     end
 
     def fetch(key, default=nil, &block)
-      if block_given?
-        config.fetch(key, &block)
+      value = fetch_for(key, default, &block)
+      if value.respond_to?(:call)
+        set(key, value.call)
       else
-        config.fetch(key, default)
+        value
       end
     end
 
@@ -55,6 +61,55 @@ module Capistrano
       @config ||= Hash.new
     end
 
+    def fetch_for(key, default, &block)
+      if block_given?
+        config.fetch(key, &block)
+      else
+        config.fetch(key, default)
+      end
+    end
+
+    class Question
+
+      def initialize(env, key, default)
+        @env, @key, @default = env, key, default
+      end
+
+      def call
+        ask_question
+        save_response
+      end
+
+      private
+      attr_reader :env, :key, :default
+
+      def ask_question
+        $stdout.puts question
+      end
+
+      def save_response
+        env.set(key, value)
+      end
+
+      def value
+        if response.empty?
+          default
+        else
+          response
+        end
+      end
+
+      def response
+        @response ||= $stdin.gets.chomp
+      end
+
+      def set(key, value)
+      end
+
+      def question
+        I18n.t(:question, key: key, default_value: default, scope: :capistrano)
+      end
+    end
 
     class Roles
       include Enumerable

lib/capistrano/dsl/env.rb

@@ -14,6 +14,10 @@ module Capistrano
         env.set(key, value)
       end
 
+      def ask(key, value)
+        env.ask(key, value)
+      end
+
       def role(name, servers)
         env.role(name, servers)
       end

lib/capistrano/i18n.rb

@@ -11,6 +11,7 @@ en = {
   finished: 'Finished',
   stage_not_set: 'Stage not set',
   written_file: 'create %{file}',
+  question: 'Please enter %{key}: |%{default_value}|',
   console: {
     welcome: 'capistrano console - enter command to execute on %{stage}',
     bye: 'bye'

lib/capistrano/templates/deploy.rb.erb

@@ -4,8 +4,7 @@ set :deploy_to, '/var/www/my_app'
 set :scm, :git
 set :repo, 'git@example.com:me/my_repo.git'
 
-set :migrations, :migrate
-set :branch, :master
+ask :branch, :master
 
 set :linked_files, %w{config/database.yml}
 set :linked_dirs, %w{bin log tmp/pids tmp/cache tmp/sockets vendor/bundle public/system}

spec/lib/capistrano/configuration_spec.rb

@@ -98,10 +98,69 @@ module Capistrano
       end
 
       context 'block is passed' do
-        subject { config.fetch(:key, :default) { :block } }
+        subject { config.fetch(:key, :default) { fail 'we need this!' } }
 
         it 'returns the block value' do
-          expect(subject).to eq :block
+          expect { subject }.to raise_error
+        end
+      end
+    end
+
+    describe 'asking' do
+      let(:question) { stub }
+
+      before do
+        Configuration::Question.expects(:new).with(config, :branch, :default).
+          returns(question)
+      end
+
+      it 'prompts for the value when fetching' do
+        config.ask(:branch, :default)
+        expect(config.fetch(:branch)).to eq question
+      end
+    end
+  end
+
+  describe Configuration::Question do
+    let(:question) { Configuration::Question.new(env, key, default) }
+    let(:default) { :default }
+    let(:key) { :branch }
+    let(:env) { stub }
+
+    describe '.new' do
+      it 'takes a key, default' do
+        question
+      end
+    end
+
+    describe '#call' do
+      subject { question.call }
+
+      context 'value is entered' do
+        let(:branch) { 'branch' }
+
+        before do
+          $stdout.expects(:puts).with('Please enter branch: |default|')
+          $stdin.expects(:gets).returns(branch)
+        end
+
+        it 'sets the value' do
+          env.expects(:set).with(key, branch)
+          question.call
+        end
+      end
+
+      context 'value is not entered' do
+        let(:branch) { default }
+
+        before do
+          $stdout.expects(:puts).with('Please enter branch: |default|')
+          $stdin.expects(:gets).returns('')
+        end
+
+        it 'sets the default as the value' do
+          env.expects(:set).with(key, branch)
+          question.call
         end
       end
     end