In a similar vein to git git git git git, if you’re using jj and find you’ve accidentally typed one jj too many in the command line, it errors at you. In this case we’re trying to pull the id of the current changeset we’re editing:

$ jj jj show -T 'change_id.short()'
error: unrecognized subcommand 'jj'

Usage: jj [OPTIONS] <COMMAND>

For more information, try '--help'.

How annoying. Now we could solve this with a shell alias, but jj also allows us to define alias’ in the configuration (much like git!), and combined with jj util exec we should be able to have it run the rest of the line nay bother.

Thinking it through, the initial jj will be exec’d by the shell, so that’s gone already. The second jj is then evaluated as the alias, so that’s gone too. The remaining arguments passed to the alias are ["show", "-T", "change_id.short()"] so if we just exec those it’ll error trying to run show as a binary. We can avoid that by having it exec jj then the arguments from the alias.

Drop the alias in a jj config file (jj config edit is super useful for editing these, or there’s jj config set to update it from the shell) and then we can test it works.

[aliases]
# jj all the way down
jj = ["util", "exec", "jj"]

Lets try our original nested command again and see if we get to see our sweet sweet change id:

$ jj jj show -T 'change_id.short()'
error: unexpected argument '-T' found

  tip: to pass '-T' as a value, use '-- -T'

Usage: jj util exec [OPTIONS] <COMMAND> [ARGS]...

For more information, try '--help'.

Oh. Our -T argument is being interpreted by jj util exec, not by the jj command we’re running. Classic nested argument parsing when you’re trying to invoke another command. Luckily shell/exec has a solution to this, passing -- as an argument stops parsing all remaining arguments so they are passed along verbatim.

With that in mind we can amend our alias to run jj util exec and then stop interpreting any further arguments.

[aliases]
# jj all the way down
jj = ["util", "exec", "--", "jj"]

Now we should be able to see our change id without any issues, no matter how many nested jjs there are in the command!

$ jj show -T 'change_id.short()'
upvqxuzzvxtx

$ jj jj show -T 'change_id.short()'
upvqxuzzvxtx

$ jj jj jj jj jj show -T 'change_id.short()'
upvqxuzzvxtx

$ jj jj jj jj jj jj jj jj jj jj jj jj jj jj jj jj jj show -T 'change_id.short()'
upvqxuzzvxtx

Happy committing.