From 4065c1742dbcfb1105827f89a0026fe8b4578da5 Mon Sep 17 00:00:00 2001
From: Markus Reiter <me@reitermark.us>
Date: Fri, 3 Aug 2018 22:15:16 +0200
Subject: [PATCH] Add update migration for double dashes.

---
 Library/Homebrew/cmd/update-report.rb | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Library/Homebrew/cmd/update-report.rb b/Library/Homebrew/cmd/update-report.rb
index 97ba6e9279..4debfeca36 100644
--- a/Library/Homebrew/cmd/update-report.rb
+++ b/Library/Homebrew/cmd/update-report.rb
@@ -85,6 +85,7 @@ module Homebrew
     end
 
     migrate_legacy_cache_if_necessary
+    migrate_cache_entries_to_double_dashes
     migrate_legacy_keg_symlinks_if_necessary
 
     if !updated
@@ -183,6 +184,21 @@ module Homebrew
     end
   end
 
+  def migrate_cache_entries_to_double_dashes
+    HOMEBREW_CACHE.children.each do |child|
+      next unless child.file?
+
+      next unless /^(?<prefix>[^\.]+[^\-])\-(?<suffix>[^\-].*)/ =~ child.basename.to_s
+      target = HOMEBREW_CACHE/"#{prefix}--#{suffix}"
+
+      if target.exist?
+        FileUtils.rm_rf child
+      else
+        FileUtils.mv child, target, force: true
+      end
+    end
+  end
+
   def migrate_legacy_repository_if_necessary
     return unless HOMEBREW_PREFIX.to_s == "/usr/local"
     return unless HOMEBREW_REPOSITORY.to_s == "/usr/local"