[Refactor] Move exit_coder from cmd to pkg/errutil

[Laitr0n]

Checklist:

• move ExitCodeError from cmd to pkg/exitcoderpkg/errutil

nerdctl/cmd/nerdctl/start.go

Lines 187 to 190 in 0b051a5

	return ExitCodeError{
	exitCode: int(code),
	}
	}

When I refactor the container start command, I have discovered that ExitCodeError from cmd is blocking my work.

nerdctl/cmd/nerdctl/main.go

Lines 343 to 367 in 0b051a5

	type ExitCoder interface {
	error
	ExitCode() int
	}
	type ExitCodeError struct {
	error
	exitCode int
	}
	func (e ExitCodeError) ExitCode() int {
	return e.exitCode
	}
	func HandleExitCoder(err error) {
	if err == nil {
	return
	}
	if exitErr, ok := err.(ExitCoder); ok {
	os.Exit(exitErr.ExitCode())
	}
	}

Maybe we should refactor ExitCodeError first, by moving it to pkg/exitcoder. Then we can continue with our other tasks.

Signed-off-by: Laitron meetlq@outlook.com

[Laitr0n]

@AkihiroSuda @Zheaoli @djdongjin PTLA

[AkihiroSuda]

Thanks