Fix bug when it has been switched to tag.

lib/extracts_path.rb

@@ -117,7 +117,10 @@ module ExtractsPath
 
     @id = File.join(@ref, @path)
 
-    @commit = CommitDecorator.decorate(@project.repository.commit(@ref))
+    # It is used "@project.repository.commits(@ref, @path, 1, 0)",
+    # because "@project.repository.commit(@ref)" returns wrong commit when @ref is tag name.
+    commits = @project.repository.commits(@ref, @path, 1, 0)
+    @commit = CommitDecorator.decorate(commits.first)
 
     @tree = Tree.new(@commit.tree, @ref, @path)
     @tree = TreeDecorator.new(@tree)

lib/gitlab/graph/json_builder.rb

@@ -113,7 +113,7 @@ module Gitlab
 
       def include_ref?(commit)
         heads = commit.refs.select do |ref|
-          ref.is_a?(Grit::Head) or ref.is_a?(Grit::Remote)
+          ref.is_a?(Grit::Head) or ref.is_a?(Grit::Remote) or ref.is_a?(Grit::Tag)
         end
 
         heads.map! do |head|