The 7.x-1.5 release was not properly generated by drupal.org's project release system.
Instead, the 7.x-1.5 release was somehow a development snapshot of the 7.x-2.x branch.
It appears that the master git repository is being treated as the 7.x-1.x branch.
I took the quick and easy solution and moved all of the 7.x-1.x changes into the master branch.
There are no functional changes between 7.x-1.5 and 7.x-1.6 other than having the correct files and the following additional stub submodules:
- cf_db_options
- cf_settings
- cf_1x_compatibility