integration tests for piping human output to a file

- [ ] Integration testing is set up

There are various option how to do it, e.g. using examples or subcrates. Will most likely benefit from using assert_cmd and/or escargot.
- [ ] Assert that piping to a file omits any color information
- [ ] Assert that piping to a file omits any interactivity

The 'duct' crate allows spawning a command and piping its stdout/stderr to a buffer/file. I'm not sure how realistic that is (setting TERM env vars and such), so we might have to just spawn a `sh` instead.

Start by inspecting the Rust crate layout and how integration tests could be introduced; compare the mentioned assert_cmd, escargot, and duct approaches, including the possible sh-based setup. Done means tests cover piping human output to a file, confirm color information is omitted, and confirm interactivity is omitted.

Written by the indexing model from the issue text.