Added Dangerfile for ruby (#3333)

* Added Dangerfile for ruby

* rm ant.tmbundle from wlist because has license

Travis output says ant.tmbundle has license, so Im removing it from the whitelist (projects without license)

* Added sample

* New line at EOF

* Fix

* Remove bad file

lib/linguist/languages.yml

@@ -3686,6 +3686,7 @@ Ruby:
   - Berksfile
   - Brewfile
   - Buildfile
+  - Dangerfile
   - Deliverfile
   - Fastfile
   - Gemfile

samples/Ruby/filenames/Dangerfile

@@ -0,0 +1,75 @@
+# Sometimes its a README fix, or something like that - which isn't relevant for
+# including in a CHANGELOG for example
+# From https://github.com/danger/danger/blob/master/Dangerfile
+
+has_app_changes = !git.modified_files.grep(/lib/).empty?
+has_test_changes = !git.modified_files.grep(/spec/).empty?
+is_version_bump = git.modified_files.sort == ["CHANGELOG.md", "lib/danger/version.rb"].sort
+
+if has_app_changes && !has_test_changes && !is_version_bump
+  warn("Tests were not updated", sticky: false)
+end
+
+# Thanks other people!
+message(":tada:") if is_version_bump && github.pr_author != "orta"
+
+# Make a note about contributors not in the organization
+unless github.api.organization_member?('danger', github.pr_author)
+  message "@#{github.pr_author} is not a contributor yet, would you like to join the Danger org?"
+
+  # Pay extra attention if they modify the gemspec
+  if git.modified_files.include?("*.gemspec")
+    warn "External contributor has edited the Gemspec"
+  end
+end
+
+# Mainly to encourage writing up some reasoning about the PR, rather than
+# just leaving a title
+if github.pr_body.length < 5
+  fail "Please provide a summary in the Pull Request description"
+end
+
+# Let people say that this isn't worth a CHANGELOG entry in the PR if they choose
+declared_trivial = (github.pr_title + github.pr_body).include?("#trivial") || !has_app_changes
+
+if !git.modified_files.include?("CHANGELOG.md") && !declared_trivial
+  fail("Please include a CHANGELOG entry. \nYou can find it at [CHANGELOG.md](https://github.com/danger/danger/blob/master/CHANGELOG.md).", sticky: false)
+end
+
+# Docs are critical, so let's re-run the docs part of the specs and show any issues:
+core_plugins_docs = `bundle exec danger plugins lint lib/danger/danger_core/plugins/*.rb --warnings-as-errors`
+
+# If it failed, fail the build, and include markdown with the output error.
+unless $?.success?
+  # We want to strip ANSI colors for our markdown, and make paths relative
+  colourless_error = core_plugins_docs.gsub(/\e\[(\d+)(;\d+)*m/, "")
+  markdown("### Core Docs Errors \n\n#{colourless_error}")
+  fail("Failing due to documentation issues, see below.", sticky: false)
+end
+
+# Oddly enough, it's quite possible to do some testing of Danger, inside Danger
+# So, you can ignore these, if you're looking at the Dangerfile to get ideas.
+#
+# If these are all empty something has gone wrong, better to raise it in a comment
+if git.modified_files.empty? && git.added_files.empty? && git.deleted_files.empty?
+  fail "This PR has no changes at all, this is likely an issue during development."
+end
+
+# This comes from `./danger_plugins/protect_files.rb` which is automatically parsed by Danger
+files.protect_files(path: "danger.gemspec", message: ".gemspec modified", fail_build: false)
+
+# Ensure that our core plugins all have 100% documentation
+core_plugins = Dir.glob("lib/danger/danger_core/plugins/*.rb")
+core_lint_output = `bundle exec yard stats #{core_plugins.join ' '} --list-undoc --tag tags`
+
+if !core_lint_output.include?("100.00%")
+  fail "The core plugins are not at 100% doc'd - see below:", sticky: false
+  markdown "```\n#{core_lint_output}```"
+elsif core_lint_output.include? "warning"
+  warn "The core plugins are have yard warnings - see below", sticky: false
+  markdown "```\n#{core_lint_output}```"
+end
+
+junit.parse "junit-results.xml"
+junit.headers = [:file, :name]
+junit.report