Move common go-junit-report code into separate internal package

There was some code duplication between the go-junit-report binary, its
tests and the testdata/generate-golden script. This has been moved into
an internal package. The go-junit-report binary can now just focus on
flag parsing and validation, and it should be less likely that the
binary, tests and golden report generator behave differently.

testdata/generate-golden-reports.go

@@ -0,0 +1,111 @@
+//go:generate go run generate-golden-reports.go -w
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/jstemmer/go-junit-report/v2/internal/gojunitreport"
+)
+
+var verbose bool
+
+var configs = map[string]gojunitreport.Config{
+	"005-no_xml_header.txt": {SkipXMLHeader: true},
+	"006-mixed.txt":         {SkipXMLHeader: true},
+	"007-compiled_test.txt": {PackageName: "test/package"},
+}
+
+func main() {
+	var writeFiles bool
+	var id int
+	flag.BoolVar(&verbose, "v", false, "verbose logging")
+	flag.BoolVar(&writeFiles, "w", false, "write output xml files")
+	flag.IntVar(&id, "id", 0, "generate report for given id only")
+	flag.Parse()
+
+	files, err := filepath.Glob("*.txt")
+	if err != nil {
+		exitf("error listing files: %v\n", err)
+	}
+
+	var idPrefix string
+	if id > 0 {
+		idPrefix = fmt.Sprintf("%03d-", id)
+	}
+	for _, file := range files {
+		if idPrefix != "" && !strings.HasPrefix(file, idPrefix) {
+			continue
+		}
+
+		outName := outputName(file)
+		if err := createReportFromInput(file, outName, writeFiles); err != nil {
+			logf("error creating report: %v\n", err)
+			continue
+		}
+		if writeFiles {
+			logf("report written to %s\n", outName)
+		}
+	}
+}
+
+func logf(msg string, args ...interface{}) {
+	if verbose {
+		fmt.Printf(msg, args...)
+	}
+}
+
+func exitf(msg string, args ...interface{}) {
+	fmt.Fprintf(os.Stderr, msg, args...)
+	os.Exit(1)
+}
+
+func outputName(input string) string {
+	dir, name := filepath.Split(input)
+	var out string
+	if idx := strings.IndexByte(name, '-'); idx > -1 {
+		out = input[:idx+1] + "report.xml"
+	} else {
+		out = strings.TrimSuffix(name, filepath.Ext(name)) + "report.xml"
+	}
+	return filepath.Join(dir, out)
+}
+
+func createReportFromInput(inputFile, outputFile string, write bool) error {
+	in, err := os.Open(inputFile)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+
+	out := io.Discard
+	if write {
+		f, err := os.Create(outputFile)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		out = f
+	}
+
+	config := configs[inputFile]
+	config.Parser = "gotest"
+	if strings.HasSuffix(inputFile, ".gojson.txt") {
+		config.Parser = "gojson"
+	}
+
+	config.Hostname = "hostname"
+	config.TimestampFunc = func() time.Time {
+		return time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
+	}
+	config.Properties = map[string]string{"go.version": "1.0"}
+
+	_, err = config.Run(in, out)
+	return err
+}