avoid repetitive memory allocations

modules/git/foreachref/format.go

@@ -27,6 +27,10 @@ type Format struct {
 	// for each reference. fieldDelim and refDelim should be selected to not
 	// interfere with each other and to not be present in field values.
 	fieldDelim []byte
+	// fieldDelimStr is a string representation of fieldDelim. Used to save
+	// us from repetitive reallocation whenever we need the delimiter as a
+	// string.
+	fieldDelimStr string
 	// refDelim is the character sequence used to separate reference from
 	// each other in the output. fieldDelim and refDelim should be selected
 	// to not interfere with each other and to not be present in field
@@ -38,9 +42,10 @@ type Format struct {
 // git-for-each-ref(1) for available fields.
 func NewFormat(fieldNames ...string) Format {
 	return Format{
-		fieldNames: fieldNames,
-		fieldDelim: nullChar,
-		refDelim:   dualNullChar,
+		fieldNames:    fieldNames,
+		fieldDelim:    nullChar,
+		fieldDelimStr: string(nullChar),
+		refDelim:      dualNullChar,
 	}
 }
 

modules/git/foreachref/parser.go

@@ -35,7 +35,7 @@ func NewParser(r io.Reader, format Format) *Parser {
 	scanner.Split(
 		func(data []byte, atEOF bool) (advance int, token []byte, err error) {
 			// Scan until delimiter, marking end of reference.
-			delimIdx := bytes.Index(data, []byte(format.refDelim))
+			delimIdx := bytes.Index(data, format.refDelim)
 			if delimIdx >= 0 {
 				token := data[:delimIdx]
 				advance := delimIdx + len(format.refDelim)
@@ -93,7 +93,7 @@ func (p *Parser) parseRef(refBlock string) (map[string]string, error) {
 
 	fieldValues := make(map[string]string)
 
-	fields := strings.Split(refBlock, string(p.format.fieldDelim))
+	fields := strings.Split(refBlock, p.format.fieldDelimStr)
 	if len(fields) != len(p.format.fieldNames) {
 		return nil, fmt.Errorf("unexpected number of reference fields: wanted %d, was %d",
 			len(fields), len(p.format.fieldNames))