-t Goal command line option would be useful

[triska]

As mentioned in #187 (comment), a -t Goal command line option would be useful.

This would allow us to invoke Scryer Prolog as:

$ scryer-prolog -g run -t halt program.pl

and have it reliably return to the shell (instead of starting the toplevel interaction), also if the specified goal fails or yields an exception.

[hurufu]

I think this feature must be well documented, because it is not immediately obvious what is the difference between "running the query" an "running the query in a toplevel".

Also you can currently use multiple -g switches:

$ scryer-prolog -g 'throw(error)' -g 'write(hello)' -g 'halt'
throw(error) causes: error
hello⏎           

[triska]

Excellent point about multiple -g switches! This could be used to solve the issue where this most recently arose (aarroyoc/doclog#9) more elegantly!

The key difference between that and the proposed -t option would be that -t lets us specify an alternative toplevel as well, to which Scryer would turn to after the goals succeed, fail or throw an exception.