add Tap#tap_migrations

This enables tap migration feature in per tap case, which will
ultimately help core/formula separation.

1 files changed, 12 insertions, 0 deletions

diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index 08e85688d..b1bc9ab0b 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -76,6 +76,7 @@ class Tap
     @alias_reverse_table = nil
     @command_files = nil
     @formula_renames = nil
+    @tap_migrations = nil
   end
 
   # The remote path to this {Tap}.
@@ -370,6 +371,17 @@ class Tap
     end
   end
 
+  # Hash with tap migrations
+  def tap_migrations
+    require "utils/json"
+
+    @tap_migrations ||= if (migration_file = path/"tap_migrations.json").file?
+      Utils::JSON.load(migration_file.read)
+    else
+      {}
+    end
+  end
+
   def ==(other)
     other = Tap.fetch(other) if other.is_a?(String)
     self.class == other.class && self.name == other.name