DestroyPromote - recursive destroy dataset, but don’t destroy any dependent clones, promote them first

- Clones get list of clones (paths) made from given dataset or snapshot
 - Get list of snapshots
 - Find snapshot (search for snapshot by name in children list)
 - IsSnapshot change signature (for simplification, hope it wan’t break lot of code)

destroy_test.go

@@ -0,0 +1,63 @@
+package zfs_test
+
+import (
+	"testing"
+
+	zfs "github.com/bicomsystems/go-libzfs"
+)
+
+func TestDataset_DestroyPromote(t *testing.T) {
+	zpoolTestPoolCreate(t)
+	// defer zpoolTestPoolDestroy(t)
+	var c1, c2 zfs.Dataset
+
+	props := make(map[zfs.Prop]zfs.Property)
+
+	d, err := zfs.DatasetCreate(TSTPoolName+"/original",
+		zfs.DatasetTypeFilesystem, make(map[zfs.Prop]zfs.Property))
+	if err != nil {
+		t.Errorf("DatasetCreate(\"%s/original\") error: %v", TSTPoolName, err)
+		return
+	}
+
+	s1, _ := zfs.DatasetSnapshot(d.Properties[zfs.DatasetPropName].Value+"@snap2", false, props)
+	s2, _ := zfs.DatasetSnapshot(d.Properties[zfs.DatasetPropName].Value+"@snap1", false, props)
+
+	c1, err = s1.Clone(TSTPoolName+"/clone1", nil)
+	if err != nil {
+		t.Errorf("d.Clone(\"%s/clone1\", props)) error: %v", TSTPoolName, err)
+		d.Close()
+		return
+	}
+
+	zfs.DatasetSnapshot(c1.Properties[zfs.DatasetPropName].Value+"@snap1", false, props)
+
+	c2, err = s2.Clone(TSTPoolName+"/clone2", nil)
+	if err != nil {
+		t.Errorf("c1.Clone(\"%s/clone1\", props)) error: %v", TSTPoolName, err)
+		d.Close()
+		c1.Close()
+		return
+	}
+	s2.Close()
+
+	zfs.DatasetSnapshot(c2.Properties[zfs.DatasetPropName].Value+"@snap0", false, props)
+	c1.Close()
+	c2.Close()
+
+	// reopen pool
+	d.Close()
+	if d, err = zfs.DatasetOpen(TSTPoolName + "/original"); err != nil {
+		t.Error("zfs.DatasetOpen")
+		return
+	}
+
+	if err = d.DestroyPromote(); err != nil {
+		t.Errorf("DestroyPromote error: %v", err)
+		d.Close()
+		return
+	}
+	t.Log("Destroy promote completed with success")
+	d.Close()
+	zpoolTestPoolDestroy(t)
+}