obshashrange: cleanup 'valid' life cycle - reset is only called when we detect a strip, the on disk data are invalid, - after a reset, we should not keep using the data base connection, - after a write, the on disk data are valid.

syntax: re
/figures/[^/]+\.png$
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
\.err$
^tests/easy_run.sh$
^build/
^dist/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$
tests/\.testtimes