Revert "Add deltifier test."

This reverts e726715a52 commit,
because reverting diff-delta emptiness change would break this test.

t/t0001-delta.sh

@@ -1,43 +0,0 @@
-#!/bin/sh
-
-test_description='Deltification regression test'
-
-../test-delta 2>/dev/null
-test $? == 127 && {
-	echo "* Skipping test-delta regression test."
-	exit 0
-}
-
-. ./test-lib.sh
-
->empty
-echo small >small
-echo smallish >smallish
-cat ../../COPYING >large
-sed -e 's/GNU/G.N.U/g' large >largish
-
-test_expect_success 'No regression in deltify code' \
-'
-fail=0
-for src in empty small smallish large largish
-do
-    for dst in empty small smallish large largish
-    do
-	if  test-delta -d $src $dst delta-$src-$dst &&
-	    test-delta -p $src delta-$src-$dst out-$src-$dst &&
-	    cmp $dst out-$src-$dst
-	then
-	    echo "* OK ($src->$dst deitify and apply)"
-	else
-	    echo "* FAIL ($src->$dst deitify and apply)"
-	    fail=1
-	fi
-    done
-done
-case "$fail" in
-0) (exit 0) ;;
-*) (exit $fail) ;;
-esac
-'
-
-test_done

test-delta.c

@@ -38,10 +38,7 @@ int main(int argc, char *argv[])
 		return 1;
 	}
 	from_size = st.st_size;
-	if (from_size)
-		from_buf = mmap(NULL, from_size, PROT_READ, MAP_PRIVATE, fd, 0);
-	else
-		from_buf = "";
+	from_buf = mmap(NULL, from_size, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (from_buf == MAP_FAILED) {
 		perror(argv[2]);
 		close(fd);
@@ -55,11 +52,7 @@ int main(int argc, char *argv[])
 		return 1;
 	}
 	data_size = st.st_size;
-
-	if (data_size)
-		data_buf = mmap(NULL, data_size, PROT_READ, MAP_PRIVATE, fd, 0);
-	else
-		data_buf = "";
+	data_buf = mmap(NULL, data_size, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (data_buf == MAP_FAILED) {
 		perror(argv[3]);
 		close(fd);