drive: add --drive-server-side-across-configs

In #2728 and 55b9a4e we decided to allow server side operations
between google drives with different configurations.

This works in some cases (eg between teamdrives) but does not work in
the general case, and this caused breakage in quite a number of
people's workflows.

This change makes the feature conditional on the
--drive-server-side-across-configs flag which defaults to off.

See: https://forum.rclone.org/t/gdrive-to-gdrive-error-404-file-not-found/9621/10

Fixes #3119

backend/drive/drive.go

@@ -382,6 +382,16 @@ will download it anyway.`,
 			Default:  defaultBurst,
 			Help:     "Number of API calls to allow without sleeping.",
 			Advanced: true,
+		}, {
+			Name:    "server_side_across_configs",
+			Default: false,
+			Help: `Allow server side operations (eg copy) to work across different drive configs.
+
+This can be useful if you wish to do a server side copy between two
+different Google drives.  Note that this isn't enabled by default
+because it isn't easy to tell if it will work beween any two
+configurations.`,
+			Advanced: true,
 		}},
 	})
 
@@ -427,6 +437,7 @@ type Options struct {
 	V2DownloadMinSize         fs.SizeSuffix `config:"v2_download_min_size"`
 	PacerMinSleep             fs.Duration   `config:"pacer_min_sleep"`
 	PacerBurst                int           `config:"pacer_burst"`
+	ServerSideAcrossConfigs   bool          `config:"server_side_across_configs"`
 }
 
 // Fs represents a remote drive server
@@ -924,7 +935,7 @@ func NewFs(name, path string, m configmap.Mapper) (fs.Fs, error) {
 		ReadMimeType:            true,
 		WriteMimeType:           true,
 		CanHaveEmptyDirectories: true,
-		ServerSideAcrossConfigs: true,
+		ServerSideAcrossConfigs: opt.ServerSideAcrossConfigs,
 	}).Fill(f)
 
 	// Create a new authorized Drive client.