Summary

Removes the magic :chain parameter from Relation#where.
It appears to be unnecessary as this method is either called with no parameters (as in where.not) or with valid parameters.
No functionality is changed

Motivation

Magic parameters are bad. In this case it makes it hard to extend the method as there is no guarantee that :chain would never be a valid argument. Say I wanted to write an extension with syntax where(:title).like('%rails%') - that would break as soon as someone had a database field called :chain

Other Information

Although I prefer avoiding magic parameters where unnecessary, the alternative is to use the object constant pattern used elsewhere in Rails. Something like

  CHAIN = Object.new
  private_constant :CHAIN
  
   def where(opts = CHAIN, *rest)
      if CHAIN == opts
     <etc>  

though, IMO, this makes the method harder to extend than simply not having it at all