Match jq exit code for no output with --exit-status

[baodrate]

For compatibility with jq's upcoming (1.7?) release.

Introduced into jq with jqlang/jq#2654, when using --exit-status, parse errors now cause jq to exit with status code 5 (JQ_ERROR_UNKNOWN) instead of 4 (JQ_OK_NO_OUTPUT). The motivation is to be able to distinguish the no-output case from parsing errors.

Mirroring this, 5 will be used for both Error::Jaq and Error::Parse, i.e. both filter parsing errors and JSON parsing errors.

[baodrate]

I also added the non-zero exit conditions to the Error enum, hoping to centralize the exit codes, and to make the exit conditional more readable. Please tell me if that's unidiomatic or otherwise subpar style though.

[01mf02]

I also added the non-zero exit conditions to the Error enum, hoping to centralize the exit codes, and to make the exit conditional more readable. Please tell me if that's unidiomatic or otherwise subpar style though.

I like your change. :)

Thanks again!