Fossil SCM

After doing a branch merge, I noticed the output has been:

$ fossil merge trunk
WARNING - no common ancestor: drivers/a.cpp
WARNING - no common ancestor: drivers/b.cpp
WARNING - no common ancestor: drivers/c.cpp
WARNING - no common ancestor: drivers/d.cpp
WARNING - no common ancestor: drivers/e.cpp
WARNING - no common ancestor: drivers/f.cpp
WARNING - no common ancestor: drivers/g.cpp
WARNING - no common ancestor: drivers/h.cpp
ADDED cmake/FindXXX.cmake
....
many ADDED/UPDATE
"fossil undo" is available to undo changes to the working checkout.
fos
$

I thought that on merge troubles, 'fossil merge' was giving a warning about the troubles at the end of the merge, but in this case it did not.

Shouldn't it give a warning, as when there are other conflicts?

Thank you.