control/controlclient: de-pointer Status.PersistView, document more

Updates #cleanup
Updates #1909

Change-Id: I31d91e120e3b299508de2136021eab3b34131a44
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/auto.go

@@ -21,7 +21,6 @@ import (
 	"tailscale.com/types/logger"
 	"tailscale.com/types/netmap"
 	"tailscale.com/types/persist"
-	"tailscale.com/types/ptr"
 	"tailscale.com/types/structs"
 )
 
@@ -644,9 +643,9 @@ func (c *Auto) sendStatus(who string, err error, url string, nm *netmap.NetworkM
 
 	c.logf("[v1] sendStatus: %s: %v", who, state)
 
-	var p *persist.PersistView
+	var p persist.PersistView
 	if nm != nil && loggedIn && synced {
-		p = ptr.To(c.direct.GetPersist())
+		p = c.direct.GetPersist()
 	} else {
 		// don't send netmap status, as it's misleading when we're
 		// not logged in.

control/controlclient/status.go

@@ -61,12 +61,24 @@ func (s State) String() string {
 }
 
 type Status struct {
-	_      structs.Incomparable
-	Err    error
-	URL    string             // interactive URL to visit to finish logging in
-	NetMap *netmap.NetworkMap // server-pushed configuration
+	_ structs.Incomparable
 
-	Persist *persist.PersistView // locally persisted configuration
+	// Err, if non-nil, is an error that occurred while logging in.
+	//
+	// If it's of type UserVisibleError then it's meant to be shown to users in
+	// their Tailscale client. Otherwise it's just logged to tailscaled's logs.
+	Err error
+
+	// URL, if non-empty, is the interactive URL to visit to finish logging in.
+	URL string
+
+	// NetMap is the latest server-pushed state of the tailnet network.
+	NetMap *netmap.NetworkMap
+
+	// Persist, when Valid, is the locally persisted configuration.
+	//
+	// TODO(bradfitz,maisem): clarify this.
+	Persist persist.PersistView
 
 	// state is the internal state. It should not be exposed outside this
 	// package, but we have some automated tests elsewhere that need to