Fix the commits are not ordered commiter date.

app/models/graph/json_builder.rb

@@ -32,7 +32,7 @@ module Graph
     #
     def collect_commits
 
-      @commits = Grit::Commit.find_all(repo, nil, {topo_order: true, max_count: self.class.max_count, skip: to_commit}).dup
+      @commits = Grit::Commit.find_all(repo, nil, {date_order: true, max_count: self.class.max_count, skip: to_commit}).dup
 
       # Decorate with app/models/commit.rb
       @commits.map! { |commit| Commit.new(commit) }
@@ -85,7 +85,7 @@ module Graph
 
     # Skip count that the target commit is displayed in center.
     def to_commit
-      commits = Grit::Commit.find_all(repo, nil, {topo_order: true})
+      commits = Grit::Commit.find_all(repo, nil, {date_order: true})
       commit_index = commits.index do |c|
         c.id == @commit.id
       end