> Could you copy/paste the --format option found in (guix scripts
> download)?

I changed it a bit.

(By the way, I'd like to add your copyright to the header of 'hash.scm'.
What year should be used?)

>> Should we capitalize error messages?

> No (info "(standards) Errors"): [...]

OK, I prepended 'guix hash' to all messages.  I'd like to change other
commands (e.g., 'guix download') accordingly.  What do you think?

I also want to change the output of 'guix download --help'.  In
particular, I'd like to specify the supported formats and remove
(default: `nix-base32').  Basically, I want it to look like the output
of 'guix hash --help'.

>> Is it OK to output a backtrace when the specified file doesn't exist?

> No, because it’s too scaring.  :-)

Done.

> Also, could you add an entry in the manual (with a couple of sentences
> explaining when users should care about this tool, and what it does), as
> well as a line in po/POTFILES.in?

Done.  But what is a translatable string?  Is it a string that should be
i18n'd?

Do you have any suggestions regarding the manual entry of 'guix hash'?
The current version looks rough to me.