anchor.diff:  Variables can also be referenced using curly braces like `${in}`.
   
   Variables might better be called "bindings", in that a given variable
  -cannot be changed, only shadowed.
  +cannot be changed, only shadowed.  More on how shadowing works
  +follows.
  +
   
   
   Rules
   ~~~~~
   
  -Rules begin with a line consisting of the `rule` keyword and a name
  -for the rule.  Then follows an indented set of `variable = value` lines.
  +Rules declare a short name for a command line.  They begin with a line
  +consisting of the `rule` keyword and a name for the rule.  Then
  +follows an indented set of `variable = value` lines.
   
   The basic example above declares a new rule named `cc`, along with the
   command to run.  (In the context of a rule, the `command` variable is
  
positive.code: 
  `depfile`:: path to an optional `Makefile` that contains extra
    _implicit dependencies_ (see the <<ref_dependencies,the reference on
    dependency types>>).  The best example is how `gcc` has the `-M`
    family of flags to output the list of headers a given `.c` file
    depends on.
  +
  ----
  rule cc
  
negative.code: 
  
  Creating .ninja files
  ---------------------
  Here's a basic `.ninja` file that demonstrates most of the syntax.
  It wil be used as an example for for the following sections.
  
  ---------------------------------
  cflags = -Wall
  