reset: trivial refactoring

After commit 3fde386 (reset [--mixed]: use diff-based reset whether or
not pathspec was given), some code can be moved to the 'reset_type ==
MIXED' check.

Let's move the code that is specific to MIXED.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
branch: trivial style fix

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
reset: trivial style cleanup

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
add: trivial style cleanup

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'fc/trivial' into pu

* fc/trivial:
  add: trivial style cleanup
  reset: trivial style cleanup
  branch: trivial style fix
  reset: trivial refactoring

Conflicts:
	builtin/reset.c