fish: and now, for an important lesson about return codes

fish/functions/fish_vcs_prompt.fish

···
     # If this is a jj repo, just note that it is one.  We don't have branches
     # in the same way as other VCSes, but it's nice to know where's jj-enabled.
     command -qs jj; and command jj root --ignore-working-copy &>/dev/null
-    if test $status -ne 1
+    if test $status -eq 0
         echo ' [jj]'
     end
 end