- `httpdate` might be worth writing from scratch, since I assume there will be edge cases and it'd be nice to know which specific cases we handle. This is not a very active dependency so I'd prefer to not take it on.
- Could we specify an expected checksum (sha256, sha512, md5) on the CLI? How would this scale if we accept multiple transfers?
- Errors documentation (and generally run cargo clippy).
- Generate manpages with https://github.com/clap-rs/clap/tree/master/clap_mangen