1 files changed, 49 insertions, 0 deletions
diff --git a/Library/Homebrew/cmd/update-report.rb b/Library/Homebrew/cmd/update-report.rb
index 9339a63d9..e11cd647b 100644
--- a/Library/Homebrew/cmd/update-report.rb
+++ b/Library/Homebrew/cmd/update-report.rb
@@ -2,6 +2,7 @@ require "formula_versions"
 require "migrator"
 require "formulary"
 require "descriptions"
+require "cleanup"
 
 module Homebrew
   def update_preinstall_header
@@ -69,6 +70,8 @@ module Homebrew
       updated = true
     end
 
+    migrate_legacy_cache_if_necessary
+
     if !updated
       if !ARGV.include?("--preinstall") && !ENV["HOMEBREW_UPDATE_FAILED"]
         puts "Already up-to-date."
@@ -101,6 +104,52 @@ module Homebrew
     ENV["HOMEBREW_UPDATE_BEFORE_HOMEBREW_HOMEBREW_CORE"] = revision
     ENV["HOMEBREW_UPDATE_AFTER_HOMEBREW_HOMEBREW_CORE"] = revision
   end
+
+  def migrate_legacy_cache_if_necessary
+    legacy_cache = Pathname.new "/Library/Caches/Homebrew"
+    return if HOMEBREW_CACHE.to_s == legacy_cache.to_s
+    return unless legacy_cache.directory?
+    return unless legacy_cache.readable_real?
+
+    migration_attempted_file = legacy_cache/".migration_attempted"
+    return if migration_attempted_file.exist?
+
+    return unless legacy_cache.writable_real?
+    FileUtils.touch migration_attempted_file
+
+    # Cleanup to avoid copying files unnecessarily
+    ohai "Cleaning up #{legacy_cache}..."
+    Cleanup.cleanup_cache legacy_cache
+
+    # This directory could have been compromised if it's world-writable/
+    # a symlink/owned by another user so don't copy files in those cases.
+    return if legacy_cache.world_writable?
+    return if legacy_cache.symlink?
+    return if !legacy_cache.owned? && legacy_cache.lstat.uid != 0
+
+    ohai "Migrating #{legacy_cache} to #{HOMEBREW_CACHE}..."
+    HOMEBREW_CACHE.mkpath
+    legacy_cache.cd do
+      legacy_cache.entries.each do |f|
+        next if [".", "..", ".migration_attempted"].include? "#{f}"
+        begin
+          FileUtils.cp_r f, HOMEBREW_CACHE
+        rescue
+          @migration_failed ||= true
+        end
+      end
+    end
+
+    if @migration_failed
+      opoo <<-EOS.undent
+        Failed to migrate #{legacy_cache} to
+        #{HOMEBREW_CACHE}. Please do so manually.
+      EOS
+    else
+      ohai "Deleting #{legacy_cache}..."
+      FileUtils.rm_rf legacy_cache
+    end
+  end
 end
 
 class Reporter