vendor: add buildkit

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

vendor/github.com/tonistiigi/fsutil/validator.go

@@ -0,0 +1,92 @@
+package fsutil
+
+import (
+	"os"
+	"path"
+	"runtime"
+	"sort"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+type parent struct {
+	dir  string
+	last string
+}
+
+type Validator struct {
+	parentDirs []parent
+}
+
+func (v *Validator) HandleChange(kind ChangeKind, p string, fi os.FileInfo, err error) (retErr error) {
+	if err != nil {
+		return err
+	}
+	// test that all paths are in order and all parent dirs were present
+	if v.parentDirs == nil {
+		v.parentDirs = make([]parent, 1, 10)
+	}
+	if runtime.GOOS == "windows" {
+		p = strings.Replace(p, "\\", "", -1)
+	}
+	if p != path.Clean(p) {
+		return errors.Errorf("invalid unclean path %s", p)
+	}
+	if path.IsAbs(p) {
+		return errors.Errorf("abolute path %s not allowed", p)
+	}
+	dir := path.Dir(p)
+	base := path.Base(p)
+	if dir == "." {
+		dir = ""
+	}
+	if dir == ".." || strings.HasPrefix(p, "../") {
+		return errors.Errorf("invalid path: %s", p)
+	}
+
+	// find a parent dir from saved records
+	i := sort.Search(len(v.parentDirs), func(i int) bool {
+		return ComparePath(v.parentDirs[len(v.parentDirs)-1-i].dir, dir) <= 0
+	})
+	i = len(v.parentDirs) - 1 - i
+	if i != len(v.parentDirs)-1 { // skipping back to grandparent
+		v.parentDirs = v.parentDirs[:i+1]
+	}
+
+	if dir != v.parentDirs[len(v.parentDirs)-1].dir || v.parentDirs[i].last >= base {
+		return errors.Errorf("changes out of order: %q %q", p, path.Join(v.parentDirs[i].dir, v.parentDirs[i].last))
+	}
+	v.parentDirs[i].last = base
+	if kind != ChangeKindDelete && fi.IsDir() {
+		v.parentDirs = append(v.parentDirs, parent{
+			dir:  path.Join(dir, base),
+			last: "",
+		})
+	}
+	// todo: validate invalid mode combinations
+	return err
+}
+
+func ComparePath(p1, p2 string) int {
+	// byte-by-byte comparison to be compatible with str<>str
+	min := min(len(p1), len(p2))
+	for i := 0; i < min; i++ {
+		switch {
+		case p1[i] == p2[i]:
+			continue
+		case p2[i] != '/' && p1[i] < p2[i] || p1[i] == '/':
+			return -1
+		default:
+			return 1
+		}
+	}
+	return len(p1) - len(p2)
+}
+
+func min(x, y int) int {
+	if x < y {
+		return x
+	}
+	return y
+}