gitlab-runner crashes when given argument "--pull-policy" rather than "--docker-pull-policy"

Summary

gitlab-runner crashes when given argument --pull-policy rather than --docker-pull-policy

Steps to reproduce

Run gitlab-runner register --pull-policy

Actual behavior

Crash:

panic: reflect: call of reflect.Value.Type on zero Value [recovered]
        panic: reflect: call of reflect.Value.Type on zero Value

goroutine 1 [running]:
panic(0x14163a0, 0xc4204085a0)
        /usr/local/go/src/runtime/panic.go:500 +0x1a1
main.main.func1()
        /go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/main.go:32 +0x7f
panic(0x14163a0, 0xc4204085a0)
        /usr/local/go/src/runtime/panic.go:458 +0x243
reflect.Value.Type(0x0, 0x0, 0x0, 0xc42008e040, 0x14b1e31)
        /usr/local/go/src/reflect/value.go:1670 +0x224
gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/gitlab.com/ayufan/golang-cli-helpers.convertMarshal(0x0, 0x0, 0x0, 0xa, 0xc4204a32a0, 0xc4200116a0, 0xc4204a32e0, 0x511e4d)
        /go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/gitlab.com/ayufan/golang-cli-helpers/convert.go:47 +0x43
gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/gitlab.com/ayufan/golang-cli-helpers.convertToString(0x0, 0x0, 0x0, 0x0, 0x0, 0x14ff740, 0xc42041c000, 0x443f51, 0x62e6d1d9000002dc)
        /go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/gitlab.com/ayufan/golang-cli-helpers/convert.go:58 +0x5d
gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/gitlab.com/ayufan/golang-cli-helpers.StructFieldValue.String(0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/gitlab.com/ayufan/golang-cli-helpers/struct_field.go:32 +0x7b
gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/gitlab.com/ayufan/golang-cli-helpers.(*StructFieldValue).String(0xc42041c000, 0x14ff740, 0xc42041c000)
        <autogenerated>:5 +0x7a
flag.isZeroValue(0xc4204726c0, 0x0, 0x0, 0x14b1e62)
        /usr/local/go/src/flag/flag.go:393 +0x12d
flag.(*FlagSet).PrintDefaults.func1(0xc4204726c0)
        /usr/local/go/src/flag/flag.go:467 +0x1d5
flag.(*FlagSet).VisitAll(0xc420453140, 0xc4204a3588)
        /usr/local/go/src/flag/flag.go:323 +0x67
flag.(*FlagSet).PrintDefaults(0xc420453140)
        /usr/local/go/src/flag/flag.go:476 +0x46
flag.defaultUsage(0xc420453140)
        /usr/local/go/src/flag/flag.go:509 +0x96
flag.(*FlagSet).usage(0xc420453140)
        /usr/local/go/src/flag/flag.go:825 +0x55
flag.(*FlagSet).failf(0xc420453140, 0x160c34b, 0x22, 0xc4204a3790, 0x1, 0x1, 0xc4204a3738, 0x478b8e)
        /usr/local/go/src/flag/flag.go:814 +0x116
flag.(*FlagSet).parseOne(0xc420453140, 0x1, 0x0, 0x0)
        /usr/local/go/src/flag/flag.go:873 +0xad8
flag.(*FlagSet).Parse(0xc420453140, 0xc42000a120, 0xe, 0xe, 0x30458d0, 0x0)
        /usr/local/go/src/flag/flag.go:915 +0x60
gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/github.com/codegangsta/cli.Command.Run(0x15ecfaa, 0x8, 0x0, 0x0, 0x0, 0x0, 0x0, 0x15fe9ba, 0x15, 0x0, ...)
        /go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/github.com/codegangsta/cli/command.go:98 +0xc33
gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/github.com/codegangsta/cli.(*App).Run(0xc420360800, 0xc42000a100, 0x10, 0x10, 0x0, 0x0)
        /go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/github.com/codegangsta/cli/app.go:159 +0x705
main.main()
        /go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/main.go:58 +0x24f

Expected behavior

An error message.

Used GitLab Runner version

Latest docker image of gitlab/gitlab-runner:latest

@aurelienrb register command uses --docker-pull-policy flag instead of --pull-policy, because all executor-related flags are prefixed with executor name.

And the problem that Runner is crashing instead of showing the usage message while using invalid flag with subcommand is known and was reported in #1904 so I'm closing this as a duplicate :).

Status changed to closed

Yep I noticed my error, I just wanted to report the crash issue so if you already know it it's perfect :)