apply extend/os to dev-cmd/update-test

Library/Homebrew/dev-cmd/update-test.rb

@@ -2,6 +2,7 @@
 # frozen_string_literal: true
 
 require "cli/parser"
+require "extend/os/dev-cmd/update-test"
 
 module Homebrew
   extend T::Sig
@@ -60,16 +61,7 @@ module Homebrew
       elsif (date = args.before)
         Utils.popen_read("git", "rev-list", "-n1", "--before=#{date}", "origin/master").chomp
       elsif args.to_tag?
-        tags = Utils.popen_read("git", "tag", "--list", "--sort=-version:refname")
-        if tags.blank?
-          tags = if (HOMEBREW_REPOSITORY/".git/shallow").exist?
-            safe_system "git", "fetch", "--tags", "--depth=1"
-            Utils.popen_read("git", "tag", "--list", "--sort=-version:refname")
-          # TODO: Refactor and move to extend/os
-          elsif OS.linux? # rubocop:disable Homebrew/MoveToExtendOS
-            Utils.popen_read("git tag --list | sort -rV")
-          end
-        end
+        tags = git_tag
         current_tag, previous_tag, = tags.lines
         current_tag = current_tag.to_s.chomp
         odie "Could not find current tag in:\n#{tags}" if current_tag.empty?
@@ -148,4 +140,17 @@ module Homebrew
   ensure
     FileUtils.rm_rf "update-test" unless args.keep_tmp?
   end
+
+  def git_tag
+    tags = Utils.popen_read("git", "tag", "--list", "--sort=-version:refname")
+    if tags.blank?
+      tags = if (HOMEBREW_REPOSITORY/".git/shallow").exist?
+        safe_system "git", "fetch", "--tags", "--depth=1"
+        Utils.popen_read("git", "tag", "--list", "--sort=-version:refname")
+      end
+    end
+    tags
+  end
+
+  alias generic_git_tag git_tag
 end

Library/Homebrew/extend/os/dev-cmd/update-test.rb

@@ -0,0 +1,4 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "extend/os/linux/dev-cmd/update-test" if OS.linux?

Library/Homebrew/extend/os/linux/dev-cmd/update-test.rb

@@ -0,0 +1,13 @@
+# typed: false
+# frozen_string_literal: true
+
+module Homebrew
+  extend T::Sig
+
+  module_function
+
+  def git_tag
+    tags = generic_git_tag
+    Utils.popen_read("git tag --list | sort -rV") if tags.blank?
+  end
+end