exthelper: support the option argument when registering a command Largefiles uses this 5th argument with push and pull, so this will be tested in the next commit. I assume the reason for unrolling and reforming the tuple in each finalxxxsetup() is to validate that something proper was passed in when registering. But it's better to explode when decorating than during the delayed actual registration.

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

^docs/training/graphs/
^docs/training/html/
^docs/training/index.html
^docs/training/graphviz-images/
^docs/training/img/
^docs/training/output/
^docs/training/pandocfilters/