Hello,

Currently, if you have an authorized manifest available and want to run 
some command (for example htop) provided by the manifest, you need to

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$ guix shell
$ htop

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as supplying a command for guix shell makes it to not look for 
manifests, and instead simply create a empty environment.

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$ guix shell -- htop
guix shell: warning: no packages specified; creating an empty 
environment
guix shell: error: htop: command not found

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Which doesn't seems a desirable behavior to me. Could we fix it?

Thanks in advance,
Luis