When working with wiggle to easily solve rebasing
conflicts we also need to be able to easily continue,
easily see the impacted files and easily clean the
repo to avoid ending up with many .rej and .porig files.

v2: Remove -r from rm. (Lucas)
    Use -z instead of '== ""' comparison. (Lucas)
    Add documentation to the helpers. (Required by make check).

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: James Ausmus <james.ausmus@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>