tier: Add hidden --force to remove tiering command (#5031)

To ensure that the server can remove an internal tier configuration
when the tiering is unreachable or other corner cases where it is not
possible for the server to determine if the tier contains some data
or fully empty.

cmd/ilm-tier-remove.go

@@ -19,17 +19,31 @@ package cmd
 
 import (
 	"github.com/minio/cli"
+	"github.com/minio/madmin-go/v3"
 	"github.com/minio/mc/pkg/probe"
 )
 
+var adminTierRmFlags = []cli.Flag{
+	cli.BoolFlag{
+		Name:   "force",
+		Usage:  "forcefully remove the specified tier",
+		Hidden: true,
+	},
+	cli.BoolFlag{
+		Name:   "dangerous",
+		Usage:  "additional flag to be required in addition to force flag",
+		Hidden: true,
+	},
+}
+
 var adminTierRmCmd = cli.Command{
 	Name:         "remove",
 	ShortName:    "rm",
 	Usage:        "remove an empty remote tier",
 	Action:       mainAdminTierRm,
 	OnUsageError: onUsageError,
 	Before:       setGlobalsFromContext,
-	Flags:        globalFlags,
+	Flags:        append(globalFlags, adminTierRmFlags...),
 	CustomHelpTemplate: `NAME:
   {{.HelpName}} - {{.Usage}}
 
@@ -65,11 +79,15 @@ func mainAdminTierRm(ctx *cli.Context) error {
 		fatalIf(errInvalidArgument(), "Tier name can't be empty")
 	}
 
+	if ctx.Bool("force") && !ctx.Bool("dangerous") {
+		fatalIf(errInvalidArgument(), "This operation results in an irreversible disconnection from the specified remote tier. If you are really sure, retry this command with ‘--force’ and ‘--dangerous’ flags.")
+	}
+
 	// Create a new MinIO Admin Client
 	client, cerr := newAdminClient(aliasedURL)
 	fatalIf(cerr, "Unable to initialize admin connection.")
 
-	e := client.RemoveTier(globalContext, tierName)
+	e := client.RemoveTierV2(globalContext, tierName, madmin.RemoveTierOpts{Force: ctx.Bool("force")})
 	fatalIf(probe.NewError(e).Trace(args...), "Unable to remove remote tier target")
 
 	printMsg(&tierMessage{