What's the right way to have Drush make automatically add version numbers to my info files?
I have this in my makefile:

api = 2
core = 7.x

projects[drupal][version] = "7.26"

;===============================================================================
; Ctools
;===============================================================================

projects[ctools][type] = module
projects[ctools][subdir] = "contrib"
projects[ctools][download][type] = git
projects[ctools][download][revision] = e720f61
projects[ctools][download][branch] = 7.x-1.x
projects[ctools][download][full_version] = 7.x-1.x-dev


I run it like so:
drush make --working-copy --no-cache --no-core my_make_file.make

For a good overview of the drush make flags: 
http://www.drushcommands.com/drush-6x/make/make

In my case version info wasn't written because I had --no-gitinfofile in my script for some reason. I hope this helps!