Add 'bundle update --group' option

lib/bundler/cli.rb

@@ -304,11 +304,14 @@ def install
         "Use the rubygems modern index instead of the API endpoint"
     method_option "jobs", :aliases => "-j", :type => :numeric, :banner =>
       "Specify the number of jobs to run in parallel"
+    method_option "group", :aliases => "-g", :type => :array, :banner =>
+      "Update a specific group"
     def update(*gems)
       sources = Array(options[:source])
+      groups  = Array(options[:group]).map(&:to_sym)
       Bundler.ui.level = "warn" if options[:quiet]
 
-      if gems.empty? && sources.empty?
+      if gems.empty? && sources.empty? && groups.empty?
         # We're doing a full update
         Bundler.definition(true)
       else
@@ -318,6 +321,8 @@ def update(*gems)
           next if names.include?(g)
           raise GemNotFound, not_found_message(g, names)
         end
+        specs = Bundler.definition.specs_for groups
+        sources.concat(specs.map(&:name))
         Bundler.definition(:gems => gems, :sources => sources)
       end
 

spec/update/gems_spec.rb

@@ -83,6 +83,22 @@
       expect(out).not_to match(/Fetching source index/)
     end
   end
+
+  describe "with --group option" do
+    it "should update only specifed group gems" do
+      install_gemfile <<-G
+        source "file://#{gem_repo2}"
+        gem "activesupport", :group => :development
+        gem "rack"
+      G
+      update_repo2 do
+        build_gem "activesupport", "3.0"
+      end
+      bundle "update --group development"
+      should_be_installed "activesupport 3.0"
+      should_not_be_installed "rack 1.2"
+    end
+  end
 end
 
 describe "bundle update in more complicated situations" do