Cmdliner v2

[smorimoto]

No description provided.

[hhugo]

I don't understand this PR. Isn't jsoo already compatible with cmdliner v2 ?

[dbuenzli]

Also the changes have nothing to do with cmdliner. They propagate the exit code of main to let exit pick them up (which apparently was not done before).

At that point you could also replace the exit calls in the error branches by the code number so that the program has a single place where it exits.

[hhugo]

exit code fixed in #2121