If this changes in the source repo and you try to reconcile from your unmodified base you'll be in for some bad surprises (things like "no common history" error

If this changes in the source repo and you try to reconcile from your unmodified base you'll be in for some bad surprises (things like "no common history" errors in the worst of cases). This is the reasons why you have to be careful with things that change branch pointers like squashing merges.