docs(cli): added makefile and go file to create docs (#3930)

Co-authored-by: Teppei Fukuda <knqyf263@gmail.com>

go.mod

@@ -199,6 +199,7 @@ require (
 	github.com/containerd/stargz-snapshotter/estargz v0.14.3 // indirect
 	github.com/containerd/ttrpc v1.1.0 // indirect
 	github.com/containerd/typeurl v1.0.2 // indirect
+	github.com/cpuguy83/go-md2man/v2 v2.0.2 // indirect
 	github.com/cyphar/filepath-securejoin v0.2.3 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect

go.sum

@@ -674,6 +674,7 @@ github.com/coreos/pkg v0.0.0-20160727233714-3ac0863d7acf/go.mod h1:E3G3o1h8I7cfc
 github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
 github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
 github.com/cpuguy83/go-md2man/v2 v2.0.0/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
+github.com/cpuguy83/go-md2man/v2 v2.0.2 h1:p1EgwI/C7NhT0JmVkwCD2ZBK8j4aeHQX2pMHHBfMQ6w=
 github.com/cpuguy83/go-md2man/v2 v2.0.2/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/creack/pty v1.1.7/go.mod h1:lj5s0c3V2DBrqTV7llrYr5NG6My20zk30Fl46Y7DoTY=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=

magefiles/magefile.go

@@ -12,6 +12,9 @@ import (
 	"github.com/magefile/mage/mg"
 	"github.com/magefile/mage/sh"
 	"github.com/magefile/mage/target"
+	"github.com/spf13/cobra/doc"
+
+	"github.com/aquasecurity/trivy/pkg/commands"
 )
 
 var (
@@ -356,7 +359,15 @@ func (Docs) Serve() error {
 
 // Generate generates CLI references
 func (Docs) Generate() error {
-	// TODO
+	ver, err := version()
+	if err != nil {
+		return err
+	}
+	cmd := commands.NewApp(ver)
+	cmd.DisableAutoGenTag = true
+	if err = doc.GenMarkdownTree(cmd, "./docs/docs/references/cli"); err != nil {
+		return err
+	}
 	return nil
 }