Added Mercurial branch support with :branch option

(cherry picked from commit c41bd5a)

lib/capistrano/recipes/deploy/scm/mercurial.rb

@@ -18,7 +18,7 @@ class Mercurial < Base
         # For mercurial HEAD == tip except that it bases this assumption on what
         # tip is in the current repository (so push before you deploy)
         def head
-          "tip"
+          configuration[:branch] || "tip"
         end
 
         # Clone the repository and update to the specified changeset.
@@ -134,4 +134,4 @@ def scm_password_or_prompt
       end
     end
   end
-end
+end

test/deploy/scm/mercurial_test.rb

@@ -17,6 +17,11 @@ def test_head
     assert_equal "tip", @source.head
   end
 
+  def test_different_head
+    @config[:branch] = "staging"
+    assert_equal "staging", @source.head
+  end
+
   def test_checkout
     @config[:repository] = "http://example.com/project-hg"
     dest = "/var/www"