Add ability to fetch preflights from OCI registry to standard out (#1117)

* add oci-fetch command

cmd/preflight/cli/oci_fetch.go

@@ -0,0 +1,26 @@
+package cli
+
+import (
+	"fmt"
+
+	"github.com/replicatedhq/troubleshoot/pkg/oci"
+	"github.com/spf13/cobra"
+)
+
+func OciFetchCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "oci-fetch [URI]",
+		Args:  cobra.MinimumNArgs(1),
+		Short: "Fetch a preflight from an OCI registry and print it to standard out",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			uri := args[0]
+			data, err := oci.PullPreflightFromOCI(uri)
+			if err != nil {
+				return err
+			}
+			fmt.Println(string(data))
+			return nil
+		},
+	}
+	return cmd
+}

cmd/preflight/cli/root.go

@@ -60,6 +60,7 @@ that a cluster meets the requirements to run an application.`,
 	cobra.OnInitialize(initConfig)
 
 	cmd.AddCommand(VersionCmd())
+	cmd.AddCommand(OciFetchCmd())
 	preflight.AddFlags(cmd.PersistentFlags())
 
 	k8sutil.AddFlags(cmd.Flags())