look one-ahead when parsing the VCF records
look one-ahead when parsing the VCF records

This ensures we don't encounter a case where we divide the graph in-between
variants that are listed at the same position.

abeconnelly/vg,dnanexus-rnd/vg,abeconnelly/vg,ekg/vg,dnanexus-rnd/vg,ekg/vg,ekg/vg