Upgrade dependency to go-containerregistry third-party library

By doing so it will fix issues met when mixing source/remote registry

Close #808

vendor/github.com/containerd/continuity/fs/path.go

@@ -1,3 +1,19 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
 package fs
 
 import (
@@ -6,7 +22,6 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"strings"
 
 	"github.com/pkg/errors"
 )
@@ -31,9 +46,8 @@ func pathChange(lower, upper *currentPath) (ChangeKind, string) {
 	if upper == nil {
 		return ChangeKindDelete, lower.path
 	}
-	// TODO: compare by directory
 
-	switch i := strings.Compare(lower.path, upper.path); {
+	switch i := directoryCompare(lower.path, upper.path); {
 	case i < 0:
 		// File in lower that is not in upper
 		return ChangeKindDelete, lower.path
@@ -45,6 +59,35 @@ func pathChange(lower, upper *currentPath) (ChangeKind, string) {
 	}
 }
 
+func directoryCompare(a, b string) int {
+	l := len(a)
+	if len(b) < l {
+		l = len(b)
+	}
+	for i := 0; i < l; i++ {
+		c1, c2 := a[i], b[i]
+		if c1 == filepath.Separator {
+			c1 = byte(0)
+		}
+		if c2 == filepath.Separator {
+			c2 = byte(0)
+		}
+		if c1 < c2 {
+			return -1
+		}
+		if c1 > c2 {
+			return +1
+		}
+	}
+	if len(a) < len(b) {
+		return -1
+	}
+	if len(a) > len(b) {
+		return +1
+	}
+	return 0
+}
+
 func sameFile(f1, f2 *currentPath) (bool, error) {
 	if os.SameFile(f1.f, f2.f) {
 		return true, nil
@@ -232,12 +275,6 @@ func walkLink(root, path string, linksWalked *int) (newpath string, islink bool,
 	if err != nil {
 		return "", false, err
 	}
-	if filepath.IsAbs(newpath) && strings.HasPrefix(newpath, root) {
-		newpath = newpath[:len(root)]
-		if !strings.HasPrefix(newpath, "/") {
-			newpath = "/" + newpath
-		}
-	}
 	*linksWalked++
 	return newpath, true, nil
 }