Changelog:
==========
* Documentation fixes
* Fix --modversion with constraints.
* Reintroduce an optimization to the dependency graph walker which avoids
revisiting already visited nodes.
* Add a regression test to check that the dependency flattener is working
as expected.
Signed-off-by: Wang Mingyu <wangmy@fujitsu.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>