use cached tree map when finding files

lib/gollum/file.rb

@@ -46,13 +46,14 @@ module Gollum
     #
     # Returns a Gollum::File or nil if the file could not be found.
     def find(name, version)
-      if commit = @wiki.repo.commit(version)
-        if (blob = commit.tree / name) && blob.is_a?(Grit::Blob)
-          @blob    = blob
-          @path    = name
-          @version = commit
-          self
-        end
+      checked = name.downcase
+      map     = @wiki.tree_map_for(version)
+      sha     = @wiki.ref_map[version] || version
+      if pair = map.detect { |(path, _)| path == checked }
+        @path    = name
+        @blob    = Grit::Blob.create(@wiki.repo,   :id => pair.last, :name => ::File.basename(@path))
+        @version = Grit::Commit.create(@wiki.repo, :id => sha)
+        self
       end
     end
   end

test/test_file.rb

@@ -11,9 +11,12 @@ context "File" do
   end
 
   test "existing file" do
-    file = @wiki.file("Mordor/todo.txt")
+    commit = @wiki.repo.commits.first
+    file   = @wiki.file("Mordor/todo.txt")
     assert_equal "[ ] Write section on Ents\n", file.raw_data
-    assert_equal @wiki.repo.commits.first.id, file.version.id
+    assert_equal 'todo.txt',         file.name
+    assert_equal commit.id,          file.version.id
+    assert_equal commit.author.name, file.version.author.name
   end
 
   test "accessing tree" do