Fix refreshing (and give a warning if refreshing gives the same result)

go.mod

@@ -3,6 +3,7 @@ module gdrive-filereplacer
 go 1.16
 
 require (
+	github.com/andrew-d/go-termutil v0.0.0-20150726205930-009166a695a2
 	golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4
 	golang.org/x/oauth2 v0.0.0-20210402161424-2e8d93401602
 	google.golang.org/api v0.43.0

go.sum

@@ -38,6 +38,8 @@ cloud.google.com/go/storage v1.10.0/go.mod h1:FLPqc6j+Ki4BU591ie1oL6qBQGu2Bl/tZ9
 dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
+github.com/andrew-d/go-termutil v0.0.0-20150726205930-009166a695a2 h1:axBiC50cNZOs7ygH5BgQp4N+aYrZ2DNpWZ1KG3VOSOM=
+github.com/andrew-d/go-termutil v0.0.0-20150726205930-009166a695a2/go.mod h1:jnzFpU88PccN/tPPhCpnNU8mZphvKxYM9lLNkd8e+os=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
 github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=

main.go

@@ -2,8 +2,10 @@ package main
 
 import (
 	"encoding/json"
+	"errors"
 	"flag"
 	"fmt"
+	"github.com/andrew-d/go-termutil"
 	"golang.org/x/net/context"
 	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
@@ -56,6 +58,9 @@ func (c *TokenCache) Token() (*oauth2.Token, error) {
 		}
 	}
 	if err != nil {
+		if !termutil.Isatty(os.Stdin.Fd()) {
+			return nil, errors.New("cached token is invalid, and can't get token from web without stdin being a terminal")
+		}
 		log.Print("Could not use cached token. Getting a new token from web...")
 		tok, err = c.NewToken()
 		if err != nil {