Fix the system-tag cli help default values after #1148 (#1219)

cmd/options.go

@@ -68,8 +68,8 @@ func optionFlagSet() *pflag.FlagSet {
 	// system-tags must have a default value, but we can't specify it here, otherwiese, it will always override others.
 	// set it to nil here, and add the default in applyDefault() instead.
 	systemTagsCliHelpText := fmt.Sprintf(
-		"only include these system tags in metrics (default %s)",
-		stats.DefaultSystemTagSet,
+		"only include these system tags in metrics (default %q)",
+		stats.DefaultSystemTagSet.SetString(),
 	)
 	flags.StringSlice("system-tags", nil, systemTagsCliHelpText)
 	flags.StringSlice("tag", nil, "add a `tag` to be applied to all samples, as `[name]=[value]`")

stats/system_tag.go

@@ -60,7 +60,7 @@ func (i *SystemTagSet) Has(tag SystemTagSet) bool {
 }
 
 // Map returns the TagSet with current value from SystemTagSet
-func (i *SystemTagSet) Map() TagSet {
+func (i SystemTagSet) Map() TagSet {
 	m := TagSet{}
 	for _, tag := range SystemTagSetValues() {
 		if i.Has(tag) {
@@ -70,6 +70,17 @@ func (i *SystemTagSet) Map() TagSet {
 	return m
 }
 
+// SetString returns comma separated list of the string representation of all values in the set
+func (i SystemTagSet) SetString() string {
+	var keys []string
+	for _, tag := range SystemTagSetValues() {
+		if i.Has(tag) {
+			keys = append(keys, tag.String())
+		}
+	}
+	return strings.Join(keys, ",")
+}
+
 // ToSystemTagSet converts list of tags to SystemTagSet
 // TODO: emit error instead of discarding invalid values.
 func ToSystemTagSet(tags []string) *SystemTagSet {