audit: flag re-added tap migrations

Re 411c217844 (commitcomment-11714539)

Closes Homebrew/homebrew#40806.

Signed-off-by: Dominyk Tiller <dominyktiller@gmail.com>

Library/Homebrew/cmd/audit.rb

@@ -3,6 +3,7 @@ require "utils"
 require "extend/ENV"
 require "formula_cellar_checks"
 require "official_taps"
+require "tap_migrations"
 require "cmd/search"
 
 module Homebrew
@@ -769,6 +770,20 @@ class FormulaAuditor
     end
   end
 
+  def audit_reverse_migration
+    # Only enforce for new formula being re-added to core
+    return unless @strict
+    return unless formula.core_formula?
+
+    if TAP_MIGRATIONS.has_key?(formula.name)
+      problem <<-EOS.undent
+       #{formula.name} seems to be listed in tap_migrations.rb!
+       Please remove #{formula.name} from present tap & tap_migrations.rb
+       before submitting it to Homebrew/homebrew.
+      EOS
+    end
+  end
+
   def audit_prefix_has_contents
     return unless formula.prefix.directory?
 
@@ -823,6 +838,7 @@ class FormulaAuditor
     text.without_patch.split("\n").each_with_index { |line, lineno| audit_line(line, lineno+1) }
     audit_installed
     audit_prefix_has_contents
+    audit_reverse_migration
   end
 
   private