Fix timeout error while showing the very large repo like git repo.

app/models/network/graph.rb

@@ -66,13 +66,30 @@ module Network
     # Skip count that the target commit is displayed in center.
     def count_to_display_commit_in_center
-      commit_index = find_commits.index do |c|
-        c.id == @commit.id
+      offset = -1
+      skip = 0
+      while offset == -1
+        tmp_commits = find_commits(skip)
+        if tmp_commits.size > 0
+          index = tmp_commits.index do |c|
+            c.id == @commit.id
+          end
+
+          if index
+            # Find the target commit
+            offset = index + skip
+          else
+            skip += self.class.max_count
+          end
+        else
+          # Cant't find the target commit in the repo.
+          offset = 0
+        end
       end
-      if commit_index && (self.class.max_count / 2 < commit_index) then
+      if self.class.max_count / 2 < offset then
         # get max index that commit is displayed in the center.
-        commit_index - self.class.max_count / 2
+        offset - self.class.max_count / 2
       else
         0
       end