perf: several dragged items cross to another place as one tar stream; older agents get them one by one

internal/proto/proto.go

@@ -5,6 +5,8 @@
 // outbound requests.
 package proto
 
+import "strings"
+
 import "encoding/json"
 
 // Control poll message types (server -> agent, returned from /api/agent/poll).
@@ -372,6 +374,20 @@ type FSShipArgs struct {
 	// Conn: the files of this side are on the SSH host of this agent's file
 	// connection (an SSH file pane), not on the machine itself.
 	Conn string `json:"conn,omitempty"`
+	// More: other things of Src's folder sent in the same stream under their
+	// own names (several files dragged at once). Agents before 0.2.0 do not
+	// know it; the server sends to them one at a time.
+	More []string `json:"more,omitempty"`
+}
+
+// ShipNames is what lands at the other end: Name, then More by their names.
+func (a FSShipArgs) ShipNames() []string {
+	n := []string{a.Name}
+	for _, p := range a.More {
+		p = strings.TrimRight(p, "/")
+		n = append(n, p[strings.LastIndex(p, "/")+1:])
+	}
+	return n
 }
 
 // ShipProgress is what a sending machine reports: bytes of files sent out of