cmdrewrite: add a utility function to make sure note is of valid format Upcoming patches will add support to store a note on various evolution related commands by storing that in obsmarker. Since the obsmarker metadata field can't store things above 255 bytes, this patch introduces a function which will be used to make sure note is under 255 bytes and does not contain newlines. We don't want notes to be multilines.

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