Tests: test_scripts.sh: Test xzdiff with one operand

The _z test is skipped if gzip isn't available.

Closes: https://github.com/tukaani-project/xz/pull/258

.gitignore

@@ -74,6 +74,9 @@ coverage
 /tests/test_memlimit
 /tests/test_stream_flags
 /tests/test_vli
+/tests/xzdiff_test
+/tests/xzdiff_test.xz
+/tests/xzdiff_test_z
 /tests/xzgrep_test_1.xz
 /tests/xzgrep_test_2.xz
 /tests/xzgrep_test_output

tests/Makefile.am

@@ -86,4 +86,5 @@ endif
 
 clean-local:
 	-rm -f compress_generated_* \
-		xzgrep_test_output xzgrep_test_1.xz xzgrep_test_2.xz
+		xzgrep_test_output xzgrep_test_1.xz xzgrep_test_2.xz \
+		xzdiff_test xzdiff_test.xz xzdiff_test_z

tests/test_scripts.sh

@@ -60,6 +60,25 @@ if test "$status" != 2 ; then
 	exit 1
 fi
 
+# With one operand, the file is compared to the same name without the suffix.
+"$XZ" -dc "$preimage" > xzdiff_test
+cp "$preimage" xzdiff_test.xz
+"$XZDIFF" xzdiff_test.xz >/dev/null
+status=$?
+if test "$status" != 0 ; then
+	echo "xzdiff with one .xz operand exited with status $status != 0"
+	exit 1
+fi
+
+if gzip -c xzdiff_test > xzdiff_test_z 2>/dev/null ; then
+	"$XZDIFF" xzdiff_test_z >/dev/null
+	status=$?
+	if test "$status" != 0 ; then
+		echo "xzdiff with one _z operand exited with status $status != 0"
+		exit 1
+	fi
+fi
+
 # The exit status must be 0 when a match was found at least from one file,
 # and 1 when no match was found in any file.
 cp "$srcdir/files/good-1-lzma2-1.xz" xzgrep_test_1.xz