Fixes https://gitlab.gnome.org/GNOME/gnome-calendar/merge_requests/70
This particular changeset is important because it fixes that annoying issue of the event staying when edited out of the range (out of the month in Month view, week in Week view, etc). Commit: https://gitlab.gnome.org/GNOME/evolution/commit/3cea6c53337382330c443f50f858424ead2005b6
It's better for the project organization if we nicely organize external projects' files in contrib/, and our own files in src/.