When saving, check that the file has not changed before our last known
save before writing the file. Only overwrite external changes if asked
to force.

Co-authored-by: LeoniePhiline <22329650+LeoniePhiline@users.noreply.github.com>
Co-authored-by: Pascal Kuthe <pascal.kuthe@semimod.de>

After discussing it further, it's best to have it done every time, a
couple options can be explored to reduce false positives in the future.