$ ./pre-inst-env guix refresh mujs
Backtrace:
          14 (apply-smob/1 #<catch-closure d12200>)
In ice-9/boot-9.scm:
    705:2 13 (call-with-prompt _ _ #<procedure default-prompt-handle…>)
In ice-9/eval.scm:
    619:8 12 (_ #(#(#<directory (guile-user) daa140>)))
In guix/ui.scm:
  1639:12 11 (run-guix-command _ . _)
In ice-9/boot-9.scm:
    829:9 10 (catch _ _ #<procedure 7f096bb0d9b0 at guix/ui.scm:617…> …)
    829:9  9 (catch _ _ #<procedure 7f096bb0d9c8 at guix/ui.scm:735…> …)
In guix/scripts/refresh.scm:
    513:8  8 (_)
In guix/store.scm:
  1693:24  7 (run-with-store _ _ #:guile-for-build _ #:system _ # _)
In guix/scripts/refresh.scm:
   538:14  6 (_ _)
In srfi/srfi-1.scm:
    640:9  5 (for-each #<procedure 1ab7680 at guix/scripts/refresh.…> …)
In guix/scripts/refresh.scm:
    346:2  4 (check-for-package-update #<package mujs@1.0.5 gnu/pac…> …)
In guix/import/github.scm:
   229:25  3 (latest-release #<package mujs@1.0.5 gnu/packages/javas…>)
   172:15  2 (latest-released-version "https://git.ghostscript.com/…" …)
   143:19  1 (fetch-releases-or-tags "https://git.ghostscript.com/mu…")
    120:2  0 (github-user-slash-repository _)

guix/import/github.scm:120:2: In procedure github-user-slash-repository:
Throw to key `match-error' with args `("match" "no matching pattern" ("" "mujs.git"))'.

mujs isn't a github repo, and it looks like there's some checking to be
done somwhere to make sure that the source is actually from a github
repo before checking the github importer for an update.

-- 
Efraim Flashner   <efraim@flashner.co.il>   אפרים פלשנר
GPG key = A28B F40C 3E55 1372 662D  14F7 41AA E7DC CA3D 8351
Confidentiality cannot be guaranteed on emails sent or received unencrypted