Exit code 1 for warnings (warning vs error handling)

[ashtonian]

It would be nice if the handling around warnings and errors was more configurable ie --errors-only or --warnings-as-errors=true/false. Right now it returns an exit code 1 when there is just warnings which is treating warnings as errors. A flag would be nice.

[chdsbd]

I think we report all violations as warnings:

squawk/cli/src/reporter.rs

Lines 393 to 402 in 6437c3c

	ReportViolation {
	file: filename.into(),
	line: lineno,
	column: col,
	level: ViolationLevel::Warning,
	messages: violation.messages,
	rule_name: violation.kind,
	sql: problem_sql.into(),
	}
	})

Maybe we could mimic eslint's exit codes.

• no violations: exit 0
• violations: exit 1
• internal error (parsing error, some unknown error): exit 2