anchor.diff:  
   Ninja file reference
   --------------------
  +
   A file is a series of declarations.  A declaration can be one of:
   
   1. A rule declaration, which begins with +rule _rulename_+, and
  
positive.code: 
  4. Variables from the file that included that file using the
     `subninja` keyword.
  
negative.code: Many projects find make alone adequate for their build problems.  In
  contrast, Ninja has almost no features; just those necessary to get
  builds correct while punting most complexity to generation of the
  ninja input files.  Ninja by itself is unlikely to be useful for most
  projects.
  
  Here are some of the features ninja adds to make.  (These sorts of
  features can often be implemented using more complicated Makefiles,
  