ipython/ipython — pull request #3822 by Carreau (2013-07-29 18:48:41+00:00)
Title: add output flag to nbconvert

fixes #3799

Cannot do it only in Writer as the basename can be used in templates as it is used for resources `to map to _files`. Here is my try on it.

Also we could be good practice to catch UsageError at high level and sys.exit only in one place.

ping @jdfreder.