* guix/git-download.scm (<git-reference>)[recursive?]: New field.
  (git-fetch): Add 'inputs' variable.  Add it to the #:inputs argument
  of 'build-expression->derivation'.  Augment builder with call to
  'set-path-environment-variable', and pass #:recursive? to
  'git-fetch'.
* guix/build/git.scm (git-fetch): Add #:recursive? parameter.  Pass
  --recursive when RECURSIVE? is true, and delete all the '.git' files.