feat: allow array as cmd option

README.md

@@ -61,7 +61,7 @@ all_on_start: true     # Check all files at Guard startup.
 cli: '--rails'         # Pass arbitrary RuboCop CLI arguments.
                        # An array or string is acceptable.
                        #   default: nil
-cmd: './bin/rubocop'   # Pass custom cmd to run rubocop.
+cmd: './bin/rubocop'   # Pass custom cmd to run rubocop as String or Array.
                        #   default: rubocop
 
 hide_stdout: false     # Do not display console output (in case outputting to file).
@@ -88,6 +88,17 @@ guard :rubocop, cli: %w(--format fuubar --format html -o ./tmp/rubocop_results.h
 end
 ```
 
+### Running with Bundler
+
+guard-rubocop can be configured to run with bundler.
+Configure your Guardfile with the cmd option:
+
+``` ruby
+guard :rubocop, cmd: %w(bundle exec guard) do
+  # ...
+end
+```
+
 ## Advanced Tips
 
 If you're using a testing Guard plugin such as [`guard-rspec`](https://github.com/guard/guard-rspec) together with `guard-rubocop` in the TDD way (the red-green-refactor cycle),

lib/guard/rubocop/runner.rb

@@ -38,6 +38,7 @@ def build_command(paths)
         command << '--force-exclusion'
         command.concat(args_specified_by_user)
         command.concat(paths)
+        command.flatten
       end
 
       def should_add_default_formatter_for_console?

spec/guard/rubocop/runner_spec.rb

@@ -118,6 +118,16 @@
         end
       end
 
+      context 'when set as array' do
+        let(:options) { { cmd: %w[bundle exec rubocop] } }
+
+        it 'uses the supplied :cmd' do
+          expect(build_command[0]).to eq('bundle')
+          expect(build_command[1]).to eq('exec')
+          expect(build_command[2]).to eq('rubocop')
+        end
+      end
+
       context 'when not set' do
         it 'uses the default command' do
           expect(build_command[0]).to eq('rubocop')