Debugging source property: Unhelpgull error message: Pulling robot Failed to find package path: '/root/parts/robot/src/toto'

I am made a few snaps that seems to work. But now I am having a hard time understanding how the source parameter work. The error message gives an error path within the snap, but in that case I would like to know the path outside, the one to be copied into the snap.

I have a part configures like this

    plugin: catkin
    source: .
    source-space: toto
    source-branch: snap

in a snapcraft.yaml in a directory (git repository, a branch called snap) like this

should’t it work?
If I run snapcraft --debug: Then I see that there is nothing in parts/robot/src nothing is copied at all. I was expecting the entire “.” directory to be copied. Am I wrong?

Is there a way to make snapcraft more verbose so we know what it is looking for?

Also if I try to write an absolute path for source (instead of “.”, it cannot even find the source type. How is snap reading the “source” property?