lsf: implement 'i' format for showing object ID - fixes #1476

cmd/lsf/lsf.go

@@ -63,6 +63,7 @@ output:
     s - size
     t - modification time
     h - hash
+    i - ID of object if known
 
 So if you wanted the path, size and modification time, you would use
 --format "pst", or maybe --format "tsp" to put the path last.
@@ -138,6 +139,8 @@ func Lsf(fsrc fs.Fs, out io.Writer) error {
 			list.AddSize()
 		case 'h':
 			list.AddHash(hashType)
+		case 'i':
+			list.AddID()
 		default:
 			return errors.Errorf("Unknown format character %q", char)
 		}

fs/operations/operations.go

@@ -1420,6 +1420,16 @@ func (l *ListFormat) AddHash(ht hash.Type) {
 	})
 }
 
+// AddID adds file's ID to the output if known
+func (l *ListFormat) AddID() {
+	l.AppendOutput(func() string {
+		if do, ok := l.entry.(fs.IDer); ok {
+			return do.ID()
+		}
+		return ""
+	})
+}
+
 // AppendOutput adds string generated by specific function to printed output
 func (l *ListFormat) AppendOutput(functionToAppend func() string) {
 	if len(l.output) > 0 {

fs/operations/operations_test.go

@@ -712,6 +712,10 @@ func TestListFormat(t *testing.T) {
 	list.AddModTime()
 	assert.Equal(t, items[0].ModTime().Local().Format("2006-01-02 15:04:05"), operations.ListFormatted(&items[0], &list))
 
+	list.SetOutput(nil)
+	list.AddID()
+	_ = operations.ListFormatted(&items[0], &list) // Can't really check anything - at least it didn't panic!
+
 	list.SetOutput(nil)
 	list.AddSize()
 	assert.Equal(t, "1", operations.ListFormatted(&items[0], &list))