vendor: update buildkit to f238f1e

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

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

@@ -22,7 +22,6 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"strings"
 
 	"github.com/pkg/errors"
 )
@@ -47,9 +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
@@ -61,6 +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