This function has been copied from the "patch_pos" function in
"patch-ids.c" but an additional parameter has been added.
The new parameter is a function pointer, that is used to access the
sha1 of an element in the table.
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>