apply: apply works outside a repository

apply: apply works outside a repository

The documentation for 'git apply' talks about applying a
patch/diff to the index and to the working tree, which seems
to imply that it will not work outside a git repository.

Actually 'git patch' works outside a repository (which can
be useful especially for applying binary or rename patches that
the standard "patch" utility cannot handle), so the documentation
should mention it.

Thanks to Junio for suggesting better wording.

Signed-off-by: Björn Gustavsson <bgustavsson@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>