Merge pull request #6111 from planetscale/ss-vtctld-nocell

vtctld: make cell optional

go/vt/vtctld/api.go

@@ -287,9 +287,17 @@ func initAPI(ctx context.Context, ts *topo.Server, actions *ActionRepository, re
 
 		if cell == "local" {
 			if *localCell == "" {
-				return nil, fmt.Errorf("local cell requested, but not specified. Please set with -cell flag")
+				cells, err := ts.GetCellInfoNames(ctx)
+				if err != nil {
+					return nil, fmt.Errorf("could not fetch cell info: %v", err)
+				}
+				if len(cells) == 0 {
+					return nil, fmt.Errorf("no local cells have been created yet")
+				}
+				cell = cells[0]
+			} else {
+				cell = *localCell
 			}
-			cell = *localCell
 		}
 
 		// If a keyspace is provided then return the specified srvkeyspace.