Investigate terminal behaviour with tee

[edwardrf]

Is the current IsTerminal detection sufficient

$ defang logout
$ defang tail --since 1h | grep error

The redirection disables any interactivity (even though only stdout got redirected)

[lionello]

Need to separate stdin vs stdout checks.

[lionello]

I did defang tail --since 18h | grep something but token was expired and I wasn't prompted to log in, because of the stdout redirection.

[lionello]

defang logout
defang tail | grep hello

This should give me the option to login, written to stderr, like regular defang tail would.