anchor.diff:  ==== Don't guess ====
   
   Tundra doesn't go out of its way to support auto-configuration of toolsets or
  -guessing what compiler you want to use. For a game project, there may be
  -millions of builds between adding a new platform or configuration to a build
  -system. Tools are also very brittle and need a specific configuration to
  -produce working builds. The time it will take to support a new toolset while
  -offset the time it takes to tell the build system about it by many magnitudes.
  -
  -Tundra therefore must be told explicitly in configuration what tools to use and
  -how to run them, it never tries to auto-configure itself for your platform. If
  -you need this capability, Tundra is probably not for you.
  +guessing what compiler you want to use. It assumes you can list the
  +configurations you care for up front. This speeds up incremental builds as no
  +time is wasted scanning for tools in the environment every time.
  +
  +For a game project, there may be millions of builds between adding a new
  +platform or configuration to a build system. Tools are also very brittle and
  +need a specific configuration to produce working builds. The time it will take
  +to support a new toolset will offset the time it takes to tell the build
  +system about it by several orders of magnitude.
   
   == Hello, world ==
   
   A Tundra project needs atleast two files, one is +tundra.lua+ which specifies
   what build configurations are available for this project. Here is a sample
   minimal +tundra.lua+ file that creates a configuration +macosx-gcc+ which pulls
  -in the default +gcc+ and +mono+ toolsets:
  +in the stock +gcc+ toolset. We also say that this configuration is to be the
  +default if nothing is specified when Tundra is run on Mac OS X:
   
   -------------------------------------------------------------------------------
   Build {
       Units = "units.lua",
       Configs = {
  -        {
  +        Config {
               Name = "macosx-gcc",
               DefaultOnHost = "macosx",
  -            Tools = { "gcc", "mono" },
  +            Tools = { "gcc" },
           },
       },
   }
  
positive.code: sections are a reference of what you can place in the +Build+ block.
  Declarations within the block can appear in any order.
  
  === Units (required) ===
  
  The build block must contain a reference to a secondary file containing unit
  
negative.code: Default "HelloWorld"
  -------------------------------------------------------------------------------
  
  If we now run Tundra on this input, it will build our +HelloWorld+ executable.
  The output path shows that tundra has defaulted the variant to `debug` and the
  subvariant to `default`.
  
  -------------------------------------------------------------------------------
  $ tundra
  