util/winutil: add RegisterForRestart, allowing programs to indicate their preferences to the Windows restart manager

In order for the installer to restart the GUI correctly post-upgrade, we
need the GUI to be able to register its restart preferences.

This PR adds API support for doing so. I'm adding it to OSS so that it
is available should we need to do any such registrations on OSS binaries
in the future.

Updates https://github.com/tailscale/corp/issues/13998

Signed-off-by: Aaron Klotz <aaron@tailscale.com>

util/winutil/winutil_windows.go

@@ -7,6 +7,7 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"os"
 	"os/exec"
 	"os/user"
 	"runtime"
@@ -15,6 +16,7 @@ import (
 	"time"
 	"unsafe"
 
+	"github.com/dblohm7/wingoes"
 	"golang.org/x/sys/windows"
 	"golang.org/x/sys/windows/registry"
 )
@@ -551,3 +553,58 @@ func findHomeDirInRegistry(uid string) (dir string, err error) {
 	}
 	return dir, nil
 }
+
+const (
+	_RESTART_NO_CRASH  = 1
+	_RESTART_NO_HANG   = 2
+	_RESTART_NO_PATCH  = 4
+	_RESTART_NO_REBOOT = 8
+)
+
+func registerForRestart(opts RegisterForRestartOpts) error {
+	var flags uint32
+
+	if !opts.RestartOnCrash {
+		flags |= _RESTART_NO_CRASH
+	}
+	if !opts.RestartOnHang {
+		flags |= _RESTART_NO_HANG
+	}
+	if !opts.RestartOnUpgrade {
+		flags |= _RESTART_NO_PATCH
+	}
+	if !opts.RestartOnReboot {
+		flags |= _RESTART_NO_REBOOT
+	}
+
+	var cmdLine *uint16
+	if opts.UseCmdLineArgs {
+		if len(opts.CmdLineArgs) == 0 {
+			// re-use our current args, excluding the exe name itself
+			opts.CmdLineArgs = os.Args[1:]
+		}
+
+		var b strings.Builder
+		for _, arg := range opts.CmdLineArgs {
+			if b.Len() > 0 {
+				b.WriteByte(' ')
+			}
+			b.WriteString(windows.EscapeArg(arg))
+		}
+
+		if b.Len() > 0 {
+			var err error
+			cmdLine, err = windows.UTF16PtrFromString(b.String())
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	hr := registerApplicationRestart(cmdLine, flags)
+	if e := wingoes.ErrorFromHRESULT(hr); e.Failed() {
+		return e
+	}
+
+	return nil
+}