Automatically append & at the end of calls if --stack > 1 ?

Is it reasonable to automatically append `&` to the end of the `--call` if `--stack` > 1?
I'm thinking it might be messy if it is a composite command, and only some of the intermediary commands need to be run in the background. Perhaps this could be detected by checking the call string for the presence of semicolons to determine if it is a composite call, and fall back to not appending `&` to the call string in those cases. Not really sure what the use cases look like, if it's even an issue.

Start by locating the CLI handling for `--call` and `--stack`, then inspect how command strings are assembled and launched. Determine whether appending `&` is safe for simple calls and how semicolon-containing composite calls should behave; the issue currently does not define an accepted result.

Written by the indexing model from the issue text.