Can't specify --test-arguments more than once

[cblp]

$ stack test --test-arguments "a b" --test-arguments "c d"
Invalid option `--test-arguments'

stack=1.1.2

expected: testArguments == ["a", "b", "c", "d"]

[mgsloan]

I'm not opposed to this, but what's the intended usecase? I can also see value in the reset semantics and this would be a behavior change.

We'd also need to revisit other similar flags and change their behavior for consistency with this one. For example, the flags for invoked programs - #652

[cblp]

Intended usecase:

1. Write a script with persistent arguments

   # ./test.sh
   stack test --test-arguments="--report --verbose" "$@"
   

2. Invoke it with ad hoc arguments

   ./test.sh --test-arguments="--parallel --filter=abc"
   

[mgsloan]

Makes sense! I think the resolution of this ticket should be that all command-argument like options have this combining semantics.

[snoyberg]

See #4748