link: use "off" value for unset expiry

backend/onedrive/onedrive.go

@@ -1429,7 +1429,7 @@ func (f *Fs) PublicLink(ctx context.Context, remote string, expire fs.Duration,
 		Password: f.opt.LinkPassword,
 	}
 
-	if expire < fs.Duration(time.Hour*24*365*100) {
+	if expire < fs.DurationOff {
 		expiry := time.Now().Add(time.Duration(expire))
 		share.Expiry = &expiry
 	}

cmd/link/link.go

@@ -3,7 +3,6 @@ package link
 import (
 	"context"
 	"fmt"
-	"time"
 
 	"github.com/rclone/rclone/cmd"
 	"github.com/rclone/rclone/fs"
@@ -13,7 +12,7 @@ import (
 )
 
 var (
-	expire = fs.Duration(time.Hour * 24 * 365 * 100)
+	expire = fs.DurationOff
 	unlink = false
 )