lsf: add metadata support with M flag

cmd/lsf/lsf.go

@@ -72,6 +72,7 @@ output:
     m - MimeType of object if known
     e - encrypted name
     T - tier of storage if known, e.g. "Hot" or "Cool"
+    M - Metadata of object in JSON blob format, eg {"key":"value"}
 
 So if you wanted the path, size and modification time, you would use
 ` + "`--format \"pst\"`, or maybe `--format \"tsp\"`" + ` to put the path last.
@@ -198,6 +199,9 @@ func Lsf(ctx context.Context, fsrc fs.Fs, out io.Writer) error {
 			opt.ShowOrigIDs = true
 		case 'T':
 			list.AddTier()
+		case 'M':
+			list.AddMetadata()
+			opt.Metadata = true
 		default:
 			return fmt.Errorf("unknown format character %q", char)
 		}

fs/operations/operations.go

@@ -7,6 +7,7 @@ import (
 	"encoding/base64"
 	"encoding/csv"
 	"encoding/hex"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -2154,6 +2155,21 @@ func (l *ListFormat) AddMimeType() {
 	})
 }
 
+// AddMetadata adds file's Metadata to the output if known
+func (l *ListFormat) AddMetadata() {
+	l.AppendOutput(func(entry *ListJSONItem) string {
+		metadata := entry.Metadata
+		if metadata == nil {
+			metadata = make(fs.Metadata)
+		}
+		out, err := json.Marshal(metadata)
+		if err != nil {
+			return fmt.Sprintf("Failed to read metadata: %v", err.Error())
+		}
+		return string(out)
+	})
+}
+
 // AppendOutput adds string generated by specific function to printed output
 func (l *ListFormat) AppendOutput(functionToAppend func(item *ListJSONItem) string) {
 	l.output = append(l.output, functionToAppend)

fs/operations/operations_test.go

@@ -1428,6 +1428,11 @@ func TestListFormat(t *testing.T) {
 	assert.Contains(t, list.Format(item0), "/")
 	assert.Equal(t, "inode/directory", list.Format(item1))
 
+	list.SetOutput(nil)
+	list.AddMetadata()
+	assert.Equal(t, "{}", list.Format(item0))
+	assert.Equal(t, "{}", list.Format(item1))
+
 	list.SetOutput(nil)
 	list.AddPath()
 	list.SetAbsolute(true)