Add ShellCommand module for shell command stubs

Library/Homebrew/abstract_command.rb

@@ -61,12 +61,5 @@ module Homebrew
 
     sig { abstract.void }
     def run; end
-
-    sig { void }
-    def raise_sh_command_error!
-      raise StandardError,
-            "This command is just here for completions generation. " \
-            "It's actually defined in `cmd/#{self.class.command_name}.sh` instead."
-    end
   end
 end

Library/Homebrew/shell_command.rb

@@ -0,0 +1,18 @@
+# typed: strict
+# frozen_string_literal: true
+
+module Homebrew
+  module ShellCommand
+    extend T::Helpers
+
+    requires_ancestor { AbstractCommand }
+
+    sig { void }
+    def run
+      sh_cmd_path = "#{self.class.dev_cmd? ? "dev-cmd" : "cmd"}/#{self.class.command_name}.sh"
+      raise StandardError,
+            "This command is just here for completions generation. " \
+            "It's actually defined in `#{sh_cmd_path}` instead."
+    end
+  end
+end