Add db copy and clone

pkg/package/database_common.go

@@ -0,0 +1,38 @@
+// Copyright © 2020 Ettore Di Giacinto <mudler@gentoo.org>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, see <http://www.gnu.org/licenses/>.
+
+package pkg
+
+import "github.com/pkg/errors"
+
+func clone(src, dst PackageDatabase) error {
+	for _, i := range src.World() {
+		_, err := dst.CreatePackage(i)
+		if err != nil {
+			return errors.Wrap(err, "Failed create package "+i.HumanReadableString())
+		}
+	}
+	return nil
+}
+
+func copy(src PackageDatabase) (PackageDatabase, error) {
+	dst := NewInMemoryDatabase(false)
+
+	if err := clone(src, dst); err != nil {
+		return dst, errors.Wrap(err, "Failed create temporary in-memory db")
+	}
+
+	return dst, nil
+}