add toggle for using the delta tree via cli (#4694)

#### Does this PR need a docs update or release note?

- [x] ⛔ No

#### Issue(s)

* #4690

#### Test Plan

- [x] ⚡ Unit test

src/cli/backup/onedrive.go

@@ -67,6 +67,12 @@ func addOneDriveCommands(cmd *cobra.Command) *cobra.Command {
 
 		flags.AddUserFlag(c)
 		flags.AddGenericBackupFlags(c)
+		fs.BoolVar(
+			&flags.UseDeltaTreeFV,
+			flags.UseDeltaTreeFN,
+			false,
+			"process backups using the delta tree instead of standard enumeration")
+		cobra.CheckErr(fs.MarkHidden(flags.UseDeltaTreeFN))
 
 	case listCommand:
 		c, fs = utils.AddCommand(cmd, oneDriveListCmd())

src/cli/flags/onedrive.go

@@ -12,6 +12,8 @@ const (
 	FileCreatedBeforeFN  = "file-created-before"
 	FileModifiedAfterFN  = "file-modified-after"
 	FileModifiedBeforeFN = "file-modified-before"
+
+	UseDeltaTreeFN = "use-delta-tree"
 )
 
 var (
@@ -22,6 +24,8 @@ var (
 	FileCreatedBeforeFV  string
 	FileModifiedAfterFV  string
 	FileModifiedBeforeFV string
+
+	UseDeltaTreeFV bool
 )
 
 // AddOneDriveDetailsAndRestoreFlags adds flags that are common to both the

src/cli/utils/options.go

@@ -27,6 +27,7 @@ func Control() control.Options {
 	opt.ToggleFeatures.DisableDelta = flags.DisableDeltaFV
 	opt.ToggleFeatures.DisableSlidingWindowLimiter = flags.DisableSlidingWindowLimiterFV
 	opt.ToggleFeatures.ExchangeImmutableIDs = flags.EnableImmutableIDFV
+	opt.ToggleFeatures.UseDeltaTree = flags.UseDeltaTreeFV
 	opt.Parallelism.ItemFetch = flags.FetchParallelismFV
 
 	return opt

src/pkg/control/options.go

@@ -109,4 +109,7 @@ type Toggles struct {
 	// Setting this flag switches exchange backups to fallback to the default token
 	// bucket rate limiter.
 	DisableSlidingWindowLimiter bool `json:"disableSlidingWindowLimiter"`
+
+	// see: https://github.com/alcionai/corso/issues/4688
+	UseDeltaTree bool `json:"useDeltaTree"`
 }