fixes dangerfile (#6158)

Dangerfile

@@ -1,29 +1,38 @@
 require 'json'
+require 'shellwords'
 
 if git.lines_of_code > 500
-  warn("This PR seems big, we prefer smaller PR. Please be sure this is needed and can’t be split in smaller commits.")
+  warn("This PR seems big, we prefer smaller PR. Please be sure this is needed and can't be split in smaller PRs.")
 end
 
-rubocop_output = `bundle exec rubocop --parallel`
+to_lint = git.modified_files + git.added_files
+files_to_lint = Shellwords.join(to_lint)
+
+rubocop_output = `bundle exec rubocop -f json --parallel #{files_to_lint}`
 if !rubocop_output.empty?
   offenses = JSON.parse(rubocop_output)['files']
     .select { |f| f['offenses'].any? }
 
-  fail(%{
-    This PR has multiple rubocop offenses:
+  def format_offense(offense)
+    output = "file: #{offense['path']}\n"
+    offense['offenses'].each do |o|
+      output << "#{o['message']} (line:#{o['location']['start_line']}, col:#{o['location']['start_column']})\n"
+    end
+    output << "\n"
+  end
 
-    #{offenses.join("\n")}
-  })
+  if !offenses.empty?
+    fail(%{
+      This PR has multiple rubocop offenses:\n
+      #{offenses.map { |o| format_offense(o) }.join('\n') }
+    })
+  end
 end
 
-prettier_output = `prettier --list-different "app/assets/stylesheets/**/*.scss" "app/assets/javascripts/**/*.es6" "test/javascripts/**/*.es6" "plugins/**/*.scss" "plugins/**/*.es6"`
-if !prettier_output.empty?
-  offenses = JSON.parse(prettier_output)['files']
-    .select { |f| f['offenses'].any? }
-
+prettier_offenses = `prettier --list-different #{files_to_lint}`.split('\n')
+if !prettier_offenses.empty?
   fail(%{
-    This PR has multiple prettier offenses:
-
-    #{offenses.join("\n")}
+    This PR has multiple prettier offenses (we recommend configuring prettier linting in your editor):\n
+    #{prettier_offenses.join("\n")}
   })
 end