version: embed VERSION.txt in unstamped version

Temporary measure until we switch to Go 1.18.

    $ go run ./cmd/tailscale version
    1.17.0-date.20211022
      go version: go1.17

Updates #81

Change-Id: Ic82ebffa5f46789089e5fb9810b3f29e36a47f1a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscale/depaware.txt

@@ -23,6 +23,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         go4.org/unsafe/assume-no-moving-gc                           from go4.org/intern
    W 💣 golang.zx2c4.com/wireguard/windows/tunnel/winipcfg           from tailscale.com/net/interfaces+
         inet.af/netaddr                                              from tailscale.com/cmd/tailscale/cli+
+        tailscale.com                                                from tailscale.com/version
         tailscale.com/atomicfile                                     from tailscale.com/ipn+
         tailscale.com/client/tailscale                               from tailscale.com/cmd/tailscale/cli+
         tailscale.com/client/tailscale/apitype                       from tailscale.com/client/tailscale+
@@ -130,7 +131,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         crypto/tls                                                   from github.com/tcnksm/go-httpstat+
         crypto/x509                                                  from crypto/tls+
         crypto/x509/pkix                                             from crypto/x509+
-        embed                                                        from tailscale.com/cmd/tailscale/cli
+        embed                                                        from tailscale.com/cmd/tailscale/cli+
         encoding                                                     from encoding/json+
         encoding/asn1                                                from crypto/x509+
         encoding/base64                                              from encoding/json+

cmd/tailscaled/depaware.txt

@@ -145,6 +145,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         inet.af/netstack/waiter                                      from inet.af/netstack/tcpip+
         inet.af/peercred                                             from tailscale.com/ipn/ipnserver
    W 💣 inet.af/wf                                                   from tailscale.com/wf
+        tailscale.com                                                from tailscale.com/version
         tailscale.com/atomicfile                                     from tailscale.com/ipn+
   LD    tailscale.com/chirp                                          from tailscale.com/cmd/tailscaled
         tailscale.com/client/tailscale                               from tailscale.com/derp

version-embed.go

@@ -0,0 +1,11 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package tailscaleroot embeds VERSION.txt into the binary.
+package tailscaleroot
+
+import _ "embed"
+
+//go:embed VERSION.txt
+var Version string

version/version.go

@@ -5,10 +5,20 @@
 // Package version provides the version that the binary was built at.
 package version
 
+import (
+	"strings"
+
+	tailscaleroot "tailscale.com"
+)
+
 // Long is a full version number for this build, of the form
 // "x.y.z-commithash", or "date.yyyymmdd" if no actual version was
 // provided.
-var Long = "date.20211004"
+var Long = "date.20211022"
+
+func init() {
+	Long = strings.TrimSpace(tailscaleroot.Version) + "-" + Long
+}
 
 // Short is a short version number for this build, of the form
 // "x.y.z", or "date.yyyymmdd" if no actual version was provided.