How to add dev modules to a distribution without getting security updates warnings?
Article Common Drush Make errors and their solutions has a solution for you. It seems that you should provide both branch and revision, if you want to clone exact revision and still have other info filled properly. 


projects[ctools][type] = module
projects[ctools][download][type] = git
projects[ctools][download][revision] = 747151e
projects[ctools][download][branch] = 7.x-1.x

  
  Although you're specifying both a revision and a branch, drush make is smart enough to use the more specific thing (the revision) when cloning. It just uses the branch information for other metadata (updating the .info files in the things it checked out, and for displaying the contents of the distribution on the release node).


Emphasis mine.