whittle down the different paths to the note to only one

[Robin-Haupt-1]

probably best done by analyzing the number of descendants any file has and always choosing the one with more of them as the main parent

related: #43 #29

[Robin-Haupt-1]

this will make it easier to travel up and down the tree: you wont have to scan the paths at the top to find the note just you came from. But this is only true if notes can't appear as the descendants of several notes anymore, which would require a rewrite of the path-finding engine