1 files changed, 37 insertions, 0 deletions
diff --git a/cloudinit/mergers/m_list.py b/cloudinit/mergers/m_list.py
new file mode 100644
index 00000000..208c5f52
--- /dev/null
+++ b/cloudinit/mergers/m_list.py
@@ -0,0 +1,37 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    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/>.
+
+
+class Merger(object):
+    def __init__(self, merger, opts):
+        self._merger = merger
+        self._extend = 'extend' in opts
+
+    def _on_tuple(self, value, merge_with):
+        return self._on_list(list(value), merge_with)
+
+    # On encountering a list or tuple type this action will be applied
+    # a new list will be returned, if the value to merge with is itself
+    # a list and we have been told to 'extend', then the value here will
+    # be extended with the other list.
+    def _on_list(self, value, merge_with):
+        if not self._extend or not isinstance(merge_with, (tuple, list)):
+            return merge_with
+        # Leave the original list alone...
+        value = list(value)
+        return value.extend(merge_with)