drive: Remove --drive-alternate-export in favor of exportLinks

Google engineer confirms that the new official API should works properly:
https://issuetracker.google.com/issues/36761333#comment8

backend/drive/drive.go

@@ -17,7 +17,6 @@ import (
 	"log"
 	"mime"
 	"net/http"
-	"net/url"
 	"path"
 	"sort"
 	"strconv"
@@ -70,7 +69,7 @@ const (
 	// 1<<18 is the minimum size supported by the Google uploader, and there is no maximum.
 	minChunkSize     = 256 * fs.KibiByte
 	defaultChunkSize = 8 * fs.MebiByte
-	partialFields    = "id,name,size,md5Checksum,trashed,explicitlyTrashed,modifiedTime,createdTime,mimeType,parents,webViewLink,shortcutDetails"
+	partialFields    = "id,name,size,md5Checksum,trashed,explicitlyTrashed,modifiedTime,createdTime,mimeType,parents,webViewLink,shortcutDetails,exportLinks"
 	listRGrouping    = 50   // number of IDs to search at once when using ListR
 	listRInputBuffer = 1000 // size of input buffer when using ListR
 )
@@ -354,17 +353,8 @@ date is used.`,
 		}, {
 			Name:    "alternate_export",
 			Default: false,
-			Help: `Use alternate export URLs for google documents export.,
-
-If this option is set this instructs rclone to use an alternate set of
-export URLs for drive documents.  Users have reported that the
-official export URLs can't export large documents, whereas these
-unofficial ones can.
-
-See rclone issue [#2243](https://github.com/rclone/rclone/issues/2243) for background,
-[this google drive issue](https://issuetracker.google.com/issues/36761333) and
-[this helpful post](https://www.labnol.org/internet/direct-links-for-google-drive/28356/).`,
-			Advanced: true,
+			Help:    "Deprecated: no longer needed",
+			Hide:    fs.OptionHideBoth,
 		}, {
 			Name:     "upload_cutoff",
 			Default:  defaultChunkSize,
@@ -527,7 +517,6 @@ type Options struct {
 	UseSharedDate             bool                 `config:"use_shared_date"`
 	ListChunk                 int64                `config:"list_chunk"`
 	Impersonate               string               `config:"impersonate"`
-	AlternateExport           bool                 `config:"alternate_export"`
 	UploadCutoff              fs.SizeSuffix        `config:"upload_cutoff"`
 	ChunkSize                 fs.SizeSuffix        `config:"chunk_size"`
 	AcknowledgeAbuse          bool                 `config:"acknowledge_abuse"`
@@ -1253,20 +1242,7 @@ func (f *Fs) newDocumentObject(remote string, info *drive.File, extension, expor
 	if err != nil {
 		return nil, err
 	}
-	id := actualID(info.Id)
-	url := fmt.Sprintf("%sfiles/%s/export?mimeType=%s", f.svc.BasePath, id, url.QueryEscape(mediaType))
-	if f.opt.AlternateExport {
-		switch info.MimeType {
-		case "application/vnd.google-apps.drawing":
-			url = fmt.Sprintf("https://docs.google.com/drawings/d/%s/export/%s", id, extension[1:])
-		case "application/vnd.google-apps.document":
-			url = fmt.Sprintf("https://docs.google.com/document/d/%s/export?format=%s", id, extension[1:])
-		case "application/vnd.google-apps.spreadsheet":
-			url = fmt.Sprintf("https://docs.google.com/spreadsheets/d/%s/export?format=%s", id, extension[1:])
-		case "application/vnd.google-apps.presentation":
-			url = fmt.Sprintf("https://docs.google.com/presentation/d/%s/export/%s", id, extension[1:])
-		}
-	}
+	url := info.ExportLinks[mediaType]
 	baseObject := f.newBaseObject(remote+extension, info)
 	baseObject.bytes = -1
 	baseObject.mimeType = exportMimeType

docs/content/drive.md

@@ -813,24 +813,6 @@ Impersonate this user when using a service account.
 - Type:        string
 - Default:     ""
 
-#### --drive-alternate-export
-
-Use alternate export URLs for google documents export.,
-
-If this option is set this instructs rclone to use an alternate set of
-export URLs for drive documents.  Users have reported that the
-official export URLs can't export large documents, whereas these
-unofficial ones can.
-
-See rclone issue [#2243](https://github.com/rclone/rclone/issues/2243) for background,
-[this google drive issue](https://issuetracker.google.com/issues/36761333) and
-[this helpful post](https://www.labnol.org/internet/direct-links-for-google-drive/28356/).
-
-- Config:      alternate_export
-- Env Var:     RCLONE_DRIVE_ALTERNATE_EXPORT
-- Type:        bool
-- Default:     false
-
 #### --drive-upload-cutoff
 
 Cutoff for switching to chunked upload