The t1301-shared-repo.sh testscript uses /usr/bin/stat to get the file
mode, which isn't portable.  Implement the test in shell using 'ls' as
shown by Junio.
Signed-off-by: NArjen Laarhoven <arjen@yaph.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>