rubocop/no_fileutils_rmrf: Discourage Pathname#rmtree too

- This [seems to be](https://ruby-doc.org/3.3.4/exts/pathname/Pathname.html#method-i-rmtree)
  equivalent to `FileUtils#rm_r`, so replace it with that.

Library/Homebrew/rubocops/no_fileutils_rmrf.rb

@@ -4,19 +4,24 @@
 module RuboCop
   module Cop
     module Homebrew
-      # This cop checks for the use of `FileUtils.rm_f`, `FileUtils.rm_rf`, or `FileUtils.rmtree`
-      # and recommends the non-`f` versions.
+      # This cop checks for the use of `FileUtils.rm_f`, `FileUtils.rm_rf`, or `{FileUtils,Pathname}.rmtree`
+      # and recommends the safer versions.
       class NoFileutilsRmrf < Base
         extend AutoCorrector
 
-        MSG = "Use `FileUtils.rm`, `FileUtils.rm_r` instead of `FileUtils.rm_rf`, `FileUtils.rm_f`, or `FileUtils.rmtree`."
+        MSG = "Use `FileUtils.rm` or `FileUtils.rm_r` instead of `FileUtils.rm_rf`, `FileUtils.rm_f`, " \
+              "or `{FileUtils,Pathname}.rmtree`."
 
         def_node_matcher :fileutils_rm_r_f?, <<~PATTERN
           (send (const {nil? cbase} :FileUtils) {:rm_rf :rm_f :rmtree} ...)
         PATTERN
 
+        def_node_matcher :pathname_rmtree?, <<~PATTERN
+          (send (const {nil? cbase} :Pathname) :rmtree ...)
+        PATTERN
+
         def on_send(node)
-          return unless fileutils_rm_r_f?(node)
+          return if neither_rm_rf_nor_rmtree?(node)
 
           add_offense(node) do |corrector|
             new_method = if node.method?(:rm_rf) || node.method?(:rmtree)
@@ -24,9 +29,14 @@ module RuboCop
             else
               "rm"
             end
+
             corrector.replace(node.loc.expression, "FileUtils.#{new_method}(#{node.arguments.first.source})")
           end
         end
+
+        def neither_rm_rf_nor_rmtree?(node)
+          !fileutils_rm_r_f?(node) && !pathname_rmtree?(node)
+        end
       end
     end
   end

Library/Homebrew/test/rubocops/no_fileutils_rmrf_spec.rb

@@ -61,4 +61,23 @@ RSpec.describe RuboCop::Cop::Homebrew::NoFileutilsRmrf do
       RUBY
     end
   end
+
+  describe "Pathname.rmtree" do
+    it "registers an offense" do
+      expect_offense(<<~RUBY)
+        Pathname.rmtree("path/to/directory")
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Homebrew/NoFileutilsRmrf: #{RuboCop::Cop::Homebrew::NoFileutilsRmrf::MSG}
+      RUBY
+    end
+
+    it "autocorrects" do
+      corrected = autocorrect_source(<<~RUBY)
+        Pathname.rmtree("path/to/directory")
+      RUBY
+
+      expect(corrected).to eq(<<~RUBY)
+        FileUtils.rm_r("path/to/directory")
+      RUBY
+    end
+  end
 end