cmd/tailscale/cli: [serve] add reset flag

Usage: `tailscale serve reset`

Fixes #8139

Signed-off-by: Sonia Appasamy <sonia@tailscale.com>

cmd/tailscale/cli/serve.go

@@ -40,6 +40,7 @@ serve https:<port> <mount-point> <source> [off]
   serve tcp:<port> tcp://localhost:<local-port> [off]
   serve tls-terminated-tcp:<port> tcp://localhost:<local-port> [off]
   serve status [--json]
+  serve reset
 `),
 		LongHelp: strings.TrimSpace(`
 *** BETA; all of this is subject to change ***
@@ -87,6 +88,13 @@ EXAMPLES
 				}),
 				UsageFunc: usageFunc,
 			},
+			{
+				Name:      "reset",
+				Exec:      e.runServeReset,
+				ShortHelp: "reset current serve/funnel config",
+				FlagSet:   e.newFlags("serve-reset", nil),
+				UsageFunc: usageFunc,
+			},
 		},
 	}
 }
@@ -705,3 +713,15 @@ func elipticallyTruncate(s string, max int) string {
 	}
 	return s[:max-3] + "..."
 }
+
+// runServeReset clears out the current serve config.
+//
+// Usage:
+//   - tailscale serve reset
+func (e *serveEnv) runServeReset(ctx context.Context, args []string) error {
+	if len(args) != 0 {
+		return flag.ErrHelp
+	}
+	sc := new(ipn.ServeConfig)
+	return e.lc.SetServeConfig(ctx, sc)
+}

cmd/tailscale/cli/serve_test.go

@@ -224,7 +224,10 @@ func TestServeConfigMutations(t *testing.T) {
 		command: cmd("https:443 bar https://127.0.0.1:8443"),
 		want:    nil, // nothing to save
 	})
-	add(step{reset: true})
+	add(step{ // try resetting using reset command
+		command: cmd("reset"),
+		want:    &ipn.ServeConfig{},
+	})
 	add(step{
 		command: cmd("https:443 / https+insecure://127.0.0.1:3001"),
 		want: &ipn.ServeConfig{