sunspot/sunspot — pull request #634 by austinmills (2014-11-11 06:13:14+00:00)
Title: Two additions to the Joins documentation in README.md for clarity and correctness. 

First, add the 'integer :id' field directive that's required to the PhotoContainer example, and second specify that you need a version of sunspot greater than 2.1.1 (that is, currently, HEAD). Without adding the integer :id, the example code will not work (complains about not finding :id field), and without more recent commits than v2.1.1, the join functionality will not work (complains about :target).