Repository navigation

Prune parameter-free subtrees; reach param_source through the children hook #560

Job	Run time
build (ubuntu-latest, Release)	35s
build (macos-latest, Debug)	28s
build (windows-latest, Release)	10m 4s
build (macos-latest, Release)	31s
build (windows-latest, Debug)	9m 28s
build (ubuntu-latest, Debug)	22s
	21m 28s