Fixing Tar functions to support Windows long paths.

Signed-off-by: Stefan J. Wernli <swernli@microsoft.com>

archive/archive.go

@@ -405,6 +405,10 @@ func Tar(path string, compression Compression) (io.ReadCloser, error) {
 // paths are included in `options.IncludeFiles` (if non-nil) or not in `options.ExcludePatterns`.
 func TarWithOptions(srcPath string, options *TarOptions) (io.ReadCloser, error) {
 
+	// Fix the source path to work with long path names. This is a no-op
+	// on platforms other than Windows.
+	srcPath = fixVolumePathPrefix(srcPath)
+
 	patterns, patDirs, exceptions, err := fileutils.CleanPatterns(options.ExcludePatterns)
 
 	if err != nil {
@@ -474,9 +478,7 @@ func TarWithOptions(srcPath string, options *TarOptions) (io.ReadCloser, error)
 		for _, include := range options.IncludeFiles {
 			rebaseName := options.RebaseNames[include]
 
-			// We can't use filepath.Join(srcPath, include) because this will
-			// clean away a trailing "." or "/" which may be important.
-			walkRoot := strings.Join([]string{srcPath, include}, string(filepath.Separator))
+			walkRoot := getWalkRoot(srcPath, include)
 			filepath.Walk(walkRoot, func(filePath string, f os.FileInfo, err error) error {
 				if err != nil {
 					logrus.Debugf("Tar: Can't stat file %s to tar: %s", srcPath, err)

archive/archive_unix.go

@@ -6,11 +6,26 @@ import (
 	"archive/tar"
 	"errors"
 	"os"
+	"path/filepath"
 	"syscall"
 
 	"github.com/docker/docker/pkg/system"
 )
 
+// fixVolumePathPrefix does platform specific processing to ensure that if
+// the path being passed in is not in a volume path format, convert it to one.
+func fixVolumePathPrefix(srcPath string) string {
+	return srcPath
+}
+
+// getWalkRoot calculates the root path when performing a TarWithOptions.
+// We use a seperate function as this is platform specific. On Linux, we
+// can't use filepath.Join(srcPath,include) because this will clean away
+// a trailing "." or "/" which may be important.
+func getWalkRoot(srcPath string, include string) string {
+	return srcPath + string(filepath.Separator) + include
+}
+
 // CanonicalTarNameForPath returns platform-specific filepath
 // to canonical posix-style path for tar archival. p is relative
 // path.

archive/archive_windows.go

@@ -6,9 +6,25 @@ import (
 	"archive/tar"
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 )
 
+// fixVolumePathPrefix does platform specific processing to ensure that if
+// the path being passed in is not in a volume path format, convert it to one.
+func fixVolumePathPrefix(srcPath string) string {
+	if !strings.HasPrefix(srcPath, `\\?\`) {
+		srcPath = `\\?\` + srcPath
+	}
+	return srcPath
+}
+
+// getWalkRoot calculates the root path when performing a TarWithOptions.
+// We use a seperate function as this is platform specific.
+func getWalkRoot(srcPath string, include string) string {
+	return filepath.Join(srcPath, include)
+}
+
 // canonicalTarNameForPath returns platform-specific filepath
 // to canonical posix-style path for tar archival. p is relative
 // path.

chrootarchive/diff_windows.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/docker/docker/pkg/archive"
 )
@@ -14,6 +15,12 @@ import (
 // contents of the layer.
 func applyLayerHandler(dest string, layer archive.Reader, decompress bool) (size int64, err error) {
 	dest = filepath.Clean(dest)
+
+	// Ensure it is a Windows-style volume path
+	if !strings.HasPrefix(dest, `\\?\`) {
+		dest = `\\?\` + dest
+	}
+
 	if decompress {
 		decompressed, err := archive.DecompressStream(layer)
 		if err != nil {