Go version: Mutually exclusive flags check not working

[FluffyEscargot]

Expected Behavior

Supplying just the --cron flag or just the --once flag should work.

Current Behavior

mysql-backup exits with errors depending on the flag

ERRO[0000] error creating timer: option 'Cron' is exclusive and must not be used with Begin, Once or Frequency

ERRO[0000] error creating timer: option 'Once' is exclusive and must not be used with Begin, Cron or Frequency

Steps to Reproduce

on master branch:
./mysql-backup dump --target /backup --cron "0 0 * * *"
./mysql-backup dump --target /backup --once

via docker:
docker run -e DB_DUMP_TARGET=/backup -e DB_DUMP_CRON="0 0 * * *" databack/mysql-backup:1.0.0-rc2 dump
docker run -e DB_DUMP_TARGET=/backup -e DB_DUMP_ONCE=true databack/mysql-backup:1.0.0-rc2 dump

Possible Solution

The --beginand --frequency flags have defaults (+0 and 1440) which are loaded at the time when mutually exclusive flags are checked. Instead, check if both flags are set, before defaults are loaded.

Possible Implementation

cmd/dump.go:229 add:

	cmd.MarkFlagsMutuallyExclusive("once", "cron")
	cmd.MarkFlagsMutuallyExclusive("once", "begin")
	cmd.MarkFlagsMutuallyExclusive("once", "frequency")
	cmd.MarkFlagsMutuallyExclusive("cron", "begin")
	cmd.MarkFlagsMutuallyExclusive("cron", "frequency")

pkg/core/timer.go:44 remove:

	// validate we do not have conflicting options
	if opts.Once && (opts.Cron != "" || opts.Begin != "" || opts.Frequency != 0) {
		return nil, errors.New("option 'Once' is exclusive and must not be used with Begin, Cron or Frequency")
	}

	if opts.Cron != "" && (opts.Begin != "" || opts.Frequency != 0) {
		return nil, errors.New("option 'Cron' is exclusive and must not be used with Begin, Once or Frequency")
	}