fix .dz as a target

and add a test for this as well

ChangeLog

@@ -4,6 +4,7 @@
 - improvements to configure for python
 - remove --disable-cxx configure flag
 - python imageize preserves interpretation
+- fix dzsave as a target format 
 
 30/12/14 started 7.42.2
 - C++ required output params were broken, thanks Lovell

libvips/foreign/dzsave.c

@@ -1734,12 +1734,12 @@ vips_foreign_save_dz_build( VipsObject *object )
 {
 		GsfOutput *out;
 		GError *error = NULL;
+		char name[VIPS_PATH_MAX];
 
-		/* We can't write to dirname: gsf_outfile_stdio_new() will
-		 * make a dir called @arg1 to hold the things we make.
-		 */
+		vips_snprintf( name, VIPS_PATH_MAX, "%s/%s", 
+			dz->dirname, dz->basename ); 
 		if( !(out = (GsfOutput *) 
-			gsf_outfile_stdio_new( dz->name, &error )) ) {
+			gsf_outfile_stdio_new( name, &error )) ) {
 			vips_g_error( &error );
 			return( -1 );
 		}
@@ -1754,10 +1754,13 @@ vips_foreign_save_dz_build( VipsObject *object )
 		GsfOutput *zip;
 		GsfOutput *out2;
 		GError *error = NULL;
+		char name[VIPS_PATH_MAX];
 
 		/* This is the zip we are building. 
 		 */
-		if( !(out = gsf_output_stdio_new( dz->name, &error )) ) {
+		vips_snprintf( name, VIPS_PATH_MAX, "%s/%s.zip", 
+			dz->dirname, dz->basename ); 
+		if( !(out = gsf_output_stdio_new( name, &error )) ) {
 			vips_g_error( &error );
 			return( -1 );
 		}

test/test_formats.sh

@@ -133,6 +133,26 @@ test_loader() {
 	echo "ok"
 }
 
+# a format for which we only have a saver (eg. dzsave)
+# just run the operation and check exit status
+test_saver() {
+	oper=$1
+	in=$2
+	suffix=$3
+
+	printf "testing $oper $(basename $in) $suffix ... "
+
+	rm -rf $tmp/savertest*
+	cmd="$vips $oper $in $tmp/savertest$suffix"
+	if !  $cmd ; then
+		echo "error executing:"
+		echo "   $cmd"
+		exit 1
+	fi
+
+	echo "ok"
+}
+
 # test for file format supported
 test_supported() {
 	format=$1
@@ -192,5 +212,9 @@ if test_supported matload; then
 	test_loader $matlab_ref $matlab matlab
 fi
 
-# we have loaders but not savers for other formats, add tests here
+if test_supported dzsave; then
+	test_saver dzsave $image .zip
+	test_saver copy $image .dz
+	test_saver copy $image .dz[container=zip]
+fi