Refactor repository layout and convert build system to Mage.

This commit implements a massive refactor of the repository, and
moves the build system over to use Mage (magefile.org) which should
allow seamless building across multiple platforms.

vendor/github.com/mholt/archiver/tarxz.go

@@ -0,0 +1,105 @@
+package archiver
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/ulikunitz/xz"
+)
+
+// TarXZ is for TarXZ format
+var TarXZ xzFormat
+
+func init() {
+	RegisterFormat("TarXZ", TarXZ)
+}
+
+type xzFormat struct{}
+
+// Match returns whether filename matches this format.
+func (xzFormat) Match(filename string) bool {
+	return strings.HasSuffix(strings.ToLower(filename), ".tar.xz") ||
+		strings.HasSuffix(strings.ToLower(filename), ".txz") ||
+		isTarXz(filename)
+}
+
+// isTarXz checks the file has the xz compressed Tar format header by reading
+// its beginning block.
+func isTarXz(tarxzPath string) bool {
+	f, err := os.Open(tarxzPath)
+	if err != nil {
+		return false
+	}
+	defer f.Close()
+
+	xzr, err := xz.NewReader(f)
+	if err != nil {
+		return false
+	}
+
+	buf := make([]byte, tarBlockSize)
+	n, err := xzr.Read(buf)
+	if err != nil || n < tarBlockSize {
+		return false
+	}
+
+	return hasTarHeader(buf)
+}
+
+// Write outputs a .tar.xz file to a Writer containing
+// the contents of files listed in filePaths. File paths
+// can be those of regular files or directories. Regular
+// files are stored at the 'root' of the archive, and
+// directories are recursively added.
+func (xzFormat) Write(output io.Writer, filePaths []string) error {
+	return writeTarXZ(filePaths, output, "")
+}
+
+// Make creates a .tar.xz file at xzPath containing
+// the contents of files listed in filePaths. File
+// paths can be those of regular files or directories.
+// Regular files are stored at the 'root' of the
+// archive, and directories are recursively added.
+func (xzFormat) Make(xzPath string, filePaths []string) error {
+	out, err := os.Create(xzPath)
+	if err != nil {
+		return fmt.Errorf("error creating %s: %v", xzPath, err)
+	}
+	defer out.Close()
+
+	return writeTarXZ(filePaths, out, xzPath)
+}
+
+func writeTarXZ(filePaths []string, output io.Writer, dest string) error {
+	xzw, err := xz.NewWriter(output)
+	if err != nil {
+		return fmt.Errorf("error compressing xz: %v", err)
+	}
+	defer xzw.Close()
+
+	return writeTar(filePaths, xzw, dest)
+}
+
+// Read untars a .tar.xz file read from a Reader and decompresses
+// the contents into destination.
+func (xzFormat) Read(input io.Reader, destination string) error {
+	xzr, err := xz.NewReader(input)
+	if err != nil {
+		return fmt.Errorf("error decompressing xz: %v", err)
+	}
+
+	return Tar.Read(xzr, destination)
+}
+
+// Open untars source and decompresses the contents into destination.
+func (xzFormat) Open(source, destination string) error {
+	f, err := os.Open(source)
+	if err != nil {
+		return fmt.Errorf("%s: failed to open archive: %v", source, err)
+	}
+	defer f.Close()
+
+	return TarXZ.Read(f, destination)
+}