From 44baa3463f32ba770f5a8e93ba8ab98deefca656 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Wed, 15 Jul 2020 18:56:07 -0700
Subject: [PATCH] cmd/tailscale/cli: add initial predicate func ActLikeCLI

---
 cmd/tailscale/cli/cli.go | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/cmd/tailscale/cli/cli.go b/cmd/tailscale/cli/cli.go
index 684389ee3..1cadb0d6a 100644
--- a/cmd/tailscale/cli/cli.go
+++ b/cmd/tailscale/cli/cli.go
@@ -23,6 +23,21 @@ import (
 	"tailscale.com/safesocket"
 )
 
+// ActLikeCLI reports whether a GUI application should act like the
+// CLI based on os.Args, GOOS, the context the process is running in
+// (pty, parent PID), etc.
+func ActLikeCLI() bool {
+	if len(os.Args) < 2 {
+		// TODO: on Windows & Mac, show usage if we're being run with a pty.
+		return false
+	}
+	switch os.Args[1] {
+	case "up", "status", "netcheck":
+		return true
+	}
+	return false
+}
+
 // Run runs the CLI. The args do npot include the binary name.
 func Run(args []string) error {
 	rootfs := flag.NewFlagSet("tailscale", flag.ExitOnError)