// Copyright 2022 The Gitea Authors. All rights reserved.// SPDX-License-Identifier: MIT package foreachref import (	"encoding/hex"	"fmt"	"io"	"strings") var (	nullChar     = []byte("\x00")	dualNullChar = []byte("\x00\x00")) // Format supports specifying and parsing an output format for 'git// for-each-ref'. See See git-for-each-ref(1) for available fields.type Format struct {	// fieldNames hold %(fieldname)s to be passed to the '--format' flag of	// for-each-ref. See git-for-each-ref(1) for available fields.	fieldNames []string 	// fieldDelim is the character sequence that is used to separate fields	// 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	// values.	refDelim []byte} // NewFormat creates a forEachRefFormat using the specified fieldNames. See// git-for-each-ref(1) for available fields.func NewFormat(fieldNames ...string) Format {	return Format{		fieldNames:    fieldNames,		fieldDelim:    nullChar,		fieldDelimStr: string(nullChar),		refDelim:      dualNullChar,	}} // Flag returns a for-each-ref --format flag value that captures the fieldNames.func (f Format) Flag() string {	var formatFlag strings.Builder	for i, field := range f.fieldNames {		// field key and field value		formatFlag.WriteString(fmt.Sprintf("%s %%(%s)", field, field)) 		if i < len(f.fieldNames)-1 {			// note: escape delimiters to allow control characters as			// delimiters. For example, '%00' for null character or '%0a'			// for newline.			formatFlag.WriteString(f.hexEscaped(f.fieldDelim))		}	}	formatFlag.WriteString(f.hexEscaped(f.refDelim))	return formatFlag.String()} // Parser returns a Parser capable of parsing 'git for-each-ref' output produced// with this Format.func (f Format) Parser(r io.Reader) *Parser {	return NewParser(r, f)} // hexEscaped produces hex-escpaed characters from a string. For example, "\n\0"// would turn into "%0a%00".func (f Format) hexEscaped(delim []byte) string {	escaped := ""	for i := 0; i < len(delim); i++ {		escaped += "%" + hex.EncodeToString([]byte{delim[i]})	}	return escaped}