cmd/uplink: ability to set experimental flag from environment variable

Change-Id: I440764a54ac83e5a85e14f64843260d9c4f993fd

cmd/uplink/external.go

@@ -24,6 +24,7 @@ import (
 	"go.uber.org/zap"
 	"golang.org/x/term"
 
+	"storj.io/common/experiment"
 	"storj.io/common/rpc/rpctracing"
 	jaeger "storj.io/monkit-jaeger"
 	"storj.io/private/version"
@@ -216,6 +217,11 @@ func (ex *external) Wrap(ctx context.Context, cmd clingy.Command) (err error) {
 		}
 	}
 
+	exp := os.Getenv("STORJ_EXPERIMENTAL")
+	if exp != "" {
+		ctx = experiment.With(ctx, exp)
+	}
+
 	// N.B.: Tracing is currently disabled by default (sample == 0, traceID == 0) and is
 	// something a user can only opt into. as a result, we don't check ex.analyticsEnabled()
 	// in this if statement. If we do ever start turning on trace samples by default, we