Revert "test_cmp: diagnose incorrect arguments"

This reverts commit d572f52a; the
idea to detect that "test_cmp expect actual" was fed a misspelt
filename meant well, but when the version of Git tested exhibits a
bug, the reason why these two files do not match may be because one
of them did not get created as expected, in which case missing file
is not a sign of misspelt filename but is a genuine test failure.
Acked-by: NEric Sunshine <sunshine@sunshineco.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/test-lib-functions.sh

@@ -905,13 +905,7 @@ test_expect_code () {
 # - not all diff versions understand "-u"
 
 test_cmp() {
-	test $# -eq 2 || BUG "test_cmp requires two arguments"
-	if ! eval "$GIT_TEST_CMP" '"$@"'
-	then
-		test "x$1" = x- || test -e "$1" || BUG "test_cmp '$1' missing"
-		test "x$2" = x- || test -e "$2" || BUG "test_cmp '$2' missing"
-		return 1
-	fi
+	eval "$GIT_TEST_CMP" '"$@"'
 }
 
 # Check that the given config key has the expected value.
@@ -940,13 +934,7 @@ test_cmp_config() {
 # test_cmp_bin - helper to compare binary files
 
 test_cmp_bin() {
-	test $# -eq 2 || BUG "test_cmp_bin requires two arguments"
-	if ! cmp "$@"
-	then
-		test "x$1" = x- || test -e "$1" || BUG "test_cmp_bin '$1' missing"
-		test "x$2" = x- || test -e "$2" || BUG "test_cmp_bin '$2' missing"
-		return 1
-	fi
+	cmp "$@"
 }
 
 # Use this instead of test_cmp to compare files that contain expected and