lsjson: add --no-mimetype flag, speed up lsf

Before this changed we unconditionally fetched the MimeType. On Some
backends like s3 and swift this takes an extra transaction which meant
that `lsf` on those backends was needlessly slow.

This adds an internal option so `lsf` can declare whether it wants
MimeTypes or not depending on whether the user asked for them and an
external flag `--no-mimetype` for `lsjson`.

See: https://forum.rclone.org/t/reliably-setup-incremental-updates/14006/8

cmd/lsf/lsf.go

@@ -167,6 +167,7 @@ func Lsf(ctx context.Context, fsrc fs.Fs, out io.Writer) error {
 	list.SetAbsolute(absolute)
 	var opt = operations.ListJSONOpt{
 		NoModTime:  true,
+		NoMimeType: true,
 		DirsOnly:   dirsOnly,
 		FilesOnly:  filesOnly,
 		Recurse:    recurse,
@@ -188,6 +189,7 @@ func Lsf(ctx context.Context, fsrc fs.Fs, out io.Writer) error {
 			list.AddID()
 		case 'm':
 			list.AddMimeType()
+			opt.NoMimeType = false
 		case 'e':
 			list.AddEncrypted()
 			opt.ShowEncrypted = true

cmd/lsjson/lsjson.go

@@ -24,6 +24,7 @@ func init() {
 	flags.BoolVarP(cmdFlags, &opt.Recurse, "recursive", "R", false, "Recurse into the listing.")
 	flags.BoolVarP(cmdFlags, &opt.ShowHash, "hash", "", false, "Include hashes in the output (may take longer).")
 	flags.BoolVarP(cmdFlags, &opt.NoModTime, "no-modtime", "", false, "Don't read the modification time (can speed things up).")
+	flags.BoolVarP(cmdFlags, &opt.NoMimeType, "no-mimetype", "", false, "Don't read the mime type (can speed things up).")
 	flags.BoolVarP(cmdFlags, &opt.ShowEncrypted, "encrypted", "M", false, "Show the encrypted names.")
 	flags.BoolVarP(cmdFlags, &opt.ShowOrigIDs, "original", "", false, "Show the ID of the underlying Object.")
 	flags.BoolVarP(cmdFlags, &opt.FilesOnly, "files-only", "", false, "Show only files in the listing.")
@@ -59,7 +60,9 @@ The output is an array of Items, where each Item looks like this
 
 If --hash is not specified the Hashes property won't be emitted.
 
-If --no-modtime is specified then ModTime will be blank.
+If --no-modtime is specified then ModTime will be blank. This can speed things up on remotes where reading the ModTime takes an extra request (eg s3, swift).
+
+If --no-mimetype is specified then MimeType will be blank. This can speed things up on remotes where reading the MimeType takes an extra request (eg s3, swift).
 
 If --encrypted is not specified the Encrypted won't be emitted.
 

fs/operations/lsjson.go

@@ -71,6 +71,7 @@ func formatForPrecision(precision time.Duration) string {
 type ListJSONOpt struct {
 	Recurse       bool `json:"recurse"`
 	NoModTime     bool `json:"noModTime"`
+	NoMimeType    bool `json:"noMimeType"`
 	ShowEncrypted bool `json:"showEncrypted"`
 	ShowOrigIDs   bool `json:"showOrigIDs"`
 	ShowHash      bool `json:"showHash"`
@@ -117,11 +118,13 @@ func ListJSON(ctx context.Context, fsrc fs.Fs, remote string, opt *ListJSONOpt,
 				Path: entry.Remote(),
 				Name: path.Base(entry.Remote()),
 				Size: entry.Size(),
-				MimeType: fs.MimeTypeDirEntry(ctx, entry),
 			}
 			if !opt.NoModTime {
 				item.ModTime = Timestamp{When: entry.ModTime(ctx), Format: format}
 			}
+			if !opt.NoMimeType {
+				item.MimeType = fs.MimeTypeDirEntry(ctx, entry)
+			}
 			if cipher != nil {
 				switch entry.(type) {
 				case fs.Directory: