added test and reafctorred kernel.Build

Signed-off-by: Christian Goll <cgoll@suse.com>

internal/pkg/util/cpio.go

@@ -0,0 +1,31 @@
+package util
+
+import (
+	"io"
+	"os"
+
+	"github.com/sassoftware/go-rpmutils/cpio"
+)
+
+/*
+Opens cpio archive and returns the file list
+*/
+func CpioFiles(name string) (files []string, err error) {
+	f, err := os.Open(name)
+	if err != nil {
+		return files, err
+	}
+	defer f.Close()
+
+	reader := cpio.NewReader(f)
+	for {
+		header, err := reader.Next()
+		if err == io.EOF {
+			return files, nil
+		}
+		if err != nil {
+			return files, err
+		}
+		files = append(files, header.Filename())
+	}
+}

internal/pkg/util/util.go

@@ -421,7 +421,7 @@ func SliceAddUniqueElement(array []string, add string) []string {
 }
 
 /*
-Appends a string slice to another slice. Guarantess that the elements are uniq.
+Appends a string slice to another slice. Guarantees that the elements are uniq.
 */
 func SliceAppendUniq(array []string, add []string) []string {
 	ret := array