undo actions are in the wrong order

[Mario Ceresa]

Actions emitted into the undo script are in the wrong order:

ex:
mkdir TEST_DIR
touch TEST_DIR/TEST_FILE
rm -rf TEST_DIR

outputs:
rm TEST_DIR/TEST_FILE
mkdir TEST_DIR
rm TEST_DIR

instead of:
mkdir TEST_DIR
touch TEST_DIR/TEST_FILE
rm TEST_DIR/TEST_FILE
rmdir TEST_DIR

Even if the result is the same, the incorrect order can give problem in more complicated situations and confuses the reader of the script.

[Mario Ceresa (mrceresa)]

This behaviour originates because the changes are grouped for the entry they refer to instead of using the time of arrival