onedrive: implement --onedrive-server-side-across-configs - fixes #4058

backend/onedrive/onedrive.go

@@ -252,6 +252,16 @@ delete OneNote files or otherwise want them to show up in directory
 listing, set this option.`,
 			Default:  false,
 			Advanced: true,
+		}, {
+			Name:    "server_side_across_configs",
+			Default: false,
+			Help: `Allow server side operations (eg copy) to work across different onedrive configs.
+
+This can be useful if you wish to do a server side copy between two
+different Onedrives.  Note that this isn't enabled by default
+because it isn't easy to tell if it will work between any two
+configurations.`,
+			Advanced: true,
 		}, {
 			Name:     config.ConfigEncoding,
 			Help:     config.ConfigEncodingHelp,
@@ -308,6 +318,7 @@ type Options struct {
 	DriveID                 string               `config:"drive_id"`
 	DriveType               string               `config:"drive_type"`
 	ExposeOneNoteFiles      bool                 `config:"expose_onenote_files"`
+	ServerSideAcrossConfigs bool                 `config:"server_side_across_configs"`
 	Enc                     encoder.MultiEncoder `config:"encoding"`
 }
 
@@ -577,6 +588,7 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 		CaseInsensitive:         true,
 		ReadMimeType:            true,
 		CanHaveEmptyDirectories: true,
+		ServerSideAcrossConfigs: opt.ServerSideAcrossConfigs,
 	}).Fill(f)
 	f.srv.SetErrorHandler(errorHandler)
 
@@ -989,11 +1001,14 @@ func (f *Fs) Copy(ctx context.Context, src fs.Object, remote string) (fs.Object,
 		return nil, err
 	}
 
+	// Check we aren't overwriting a file on the same remote
+	if srcObj.fs == f {
 		srcPath := srcObj.rootPath()
 		dstPath := f.rootPath(remote)
 		if strings.ToLower(srcPath) == strings.ToLower(dstPath) {
 			return nil, errors.Errorf("can't copy %q -> %q as are same name when lowercase", srcPath, dstPath)
 		}
+	}
 
 	// Create temporary object
 	dstObj, leaf, directoryID, err := f.createObject(ctx, remote, srcObj.modTime, srcObj.size)