bug#46303: Typo helper doesn't always know which command is missing

[Leo Famulari]

On Tue, Jan 19, 2021 at 10:28:08PM +0100, zimoun wrote:
> * guix/utils.scm (string-distance): New procedure.
> (string-closest): New procedure.
> * tests/utils.scm: Test it.

This is a great feature, but I found a tricky failure:

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$ ./pre-inst-env guix system vm --no-grafts doc/os-config-bare-bones.texi 
--substitute-urls=https://ci.guix.gnu.org -d
guix: system: command not found                                                 
                                                         
hint: Did you mean `system'?

Try `guix --help' for more information.
$ guix environment guix
$ ./pre-inst-env guix system vm --no-grafts doc/os-config-bare-bones.texi -d
/gnu/store/pw453xpixcll02w1nz9mfggm2cn0jqpx-run-vm.sh.drv
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It will only be seen by developers, so not a big deal, but it would
still be nice to correctly report which command is missing. Some
run-time dependency of guix is missing.