-- takes (incorrectly) takes precedence over allowing hyphen values

[kbknapp]

See BurntSushi/ripgrep#482

The error stems from src/app/parser.rs#803 which isn't considering if we're currently parsing a value or not and whether that value allows leading hyphens.

My only concern is args like ripgrep's -e which allow multiple values, is there a case where -e -- -- arg1 would be valid? Where the second -- is meant as the true "only positional args follow". (NB ripgrep specifically actually avoids this edge case by [correctly] only allowing one value per -e invocation.)