Commit Briefs
WIP attempt to track vertex IDs with ints to save memory (topoload-with-vertex-ids)
this does not seem to work as expected, igraph' internal vertex IDs seems to change as more node get added (index 1 was a tree, checking back later it's a commit...)
use a bitstring to keep track of traversed object IDs
The aim is to reduce the memory footprint of object graph construction