+ Raise an error on install with multiple gems and --version

lib/rubygems/commands/install_command.rb

@@ -153,6 +153,12 @@ def execute
 
     exit_code = 0
 
+    if options[:version] != Gem::Requirement.default &&
+        get_all_gem_names.size > 1 then
+      alert_error "Can't use --version w/ multiple gems. Use name:ver instead."
+      terminate_interaction 1
+    end
+
     get_all_gem_names_and_versions.each do |gem_name, gem_version|
       gem_version ||= options[:version]
 

test/rubygems/test_gem_commands_install_command.rb

@@ -443,6 +443,26 @@ def test_execute_two
     assert out.empty?, out.inspect
   end
 
+  def test_execute_two_version
+    @cmd.options[:args] = %w[a b]
+    @cmd.options[:version] = Gem::Requirement.new("> 1")
+
+    use_ui @ui do
+      e = assert_raises Gem::MockGemUi::TermError do
+        @cmd.execute
+      end
+
+      assert_equal 1, e.exit_code
+    end
+
+    assert_empty @cmd.installed_specs
+
+    msg = "ERROR:  Can't use --version w/ multiple gems. Use name:ver instead."
+
+    assert_empty @ui.output
+    assert_equal msg, @ui.error.chomp
+  end
+
   def test_execute_conservative
     util_setup_fake_fetcher
     util_setup_spec_fetcher