formula_desc_cop: ensure no full stops at the end of desc

- This was a suggestion by Mike McQuaid in my `homebrew-core` audit
  description PR. Based on ilovezfs's incantation `grep -r -E 'desc
  ".*\."' *.rb`, some formulae descriptions do end in full stops. (My
  initial assessment of this failed to account for the fact that
  descriptions are strings and so end in `"`.)
- Add an autocorrect for this cop, too.

1 files changed, 10 insertions, 0 deletions

diff --git a/Library/Homebrew/test/rubocops/formula_desc_cop_spec.rb b/Library/Homebrew/test/rubocops/formula_desc_cop_spec.rb
index 3ddc42d34..aacb52ebb 100644
--- a/Library/Homebrew/test/rubocops/formula_desc_cop_spec.rb
+++ b/Library/Homebrew/test/rubocops/formula_desc_cop_spec.rb
@@ -91,6 +91,16 @@ describe RuboCop::Cop::FormulaAuditStrict::Desc do
       RUBY
     end
 
+    it "When the description ends with a full stop" do
+      expect_offense(<<~RUBY, "/homebrew-core/Formula/foo.rb")
+        class Foo < Formula
+          url 'http://example.com/foo-1.0.tgz'
+          desc 'Description with a full stop at the end.'
+                                                       ^ Description shouldn\'t end with a full stop
+        end
+      RUBY
+    end
+
     it "autocorrects all rules" do
       source = <<~EOS
         class Foo < Formula