The command `--help` text output in the book was very wide, which caused
it to be clipped and require scrolling horizontally to see it all.
This diff renders the text at 80 columns, which makes it visible without
scrolling at reasonable screen sizes.
To do this, `env::run` now checks for the presence of the environment
variable `IMDL_TERM_WIDTH`, which, if set to a positive integer, will be
passed to `Clap::set_term_width`.
`bin/man` now uses this to render the help text at 80 characters.
type: documentation
pr: https://github.com/casey/intermodal/pull/364
f05807290b