tab: allow to store versions

Library/Homebrew/tab.rb

@@ -32,7 +32,12 @@ def self.create(formula, compiler, stdlib)
       "source" => {
         "path" => formula.path.to_s,
         "tap" => formula.tap ? formula.tap.name : nil,
-        "spec" => formula.active_spec_sym.to_s
+        "spec" => formula.active_spec_sym.to_s,
+        "versions" => {
+          "stable" => formula.stable ? formula.stable.version.to_s : nil,
+          "devel" => formula.devel ? formula.devel.version.to_s : nil,
+          "head" => formula.head ? formula.head.version.to_s : nil,
+        }
       }
     }
 
@@ -68,6 +73,14 @@ def self.from_file_content(content, path)
       end
     end
 
+    if attributes["source"]["versions"].nil?
+      attributes["source"]["versions"] = {
+        "stable" => nil,
+        "devel" => nil,
+        "head" => nil,
+      }
+    end
+
     new(attributes)
   end
 
@@ -145,7 +158,12 @@ def self.empty
       "source" => {
         "path" => nil,
         "tap" => nil,
-        "spec" => "stable"
+        "spec" => "stable",
+        "versions" => {
+          "stable" => nil,
+          "devel" => nil,
+          "head" => nil,
+        }
       }
     }
 
@@ -232,6 +250,22 @@ def spec
     source["spec"].to_sym
   end
 
+  def versions
+    source["versions"]
+  end
+
+  def stable_version
+    Version.create(versions["stable"]) if versions["stable"]
+  end
+
+  def devel_version
+    Version.create(versions["devel"]) if versions["devel"]
+  end
+
+  def head_version
+    Version.create(versions["head"]) if versions["head"]
+  end
+
   def source_modified_time
     Time.at(super)
   end