vendor: add buildkit

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

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

@@ -0,0 +1,150 @@
+package fsutil
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"runtime"
+	"sort"
+	strings "strings"
+
+	"github.com/pkg/errors"
+)
+
+func FollowLinks(root string, paths []string) ([]string, error) {
+	r := &symlinkResolver{root: root, resolved: map[string]struct{}{}}
+	for _, p := range paths {
+		if err := r.append(p); err != nil {
+			return nil, err
+		}
+	}
+	res := make([]string, 0, len(r.resolved))
+	for r := range r.resolved {
+		res = append(res, r)
+	}
+	sort.Strings(res)
+	return dedupePaths(res), nil
+}
+
+type symlinkResolver struct {
+	root     string
+	resolved map[string]struct{}
+}
+
+func (r *symlinkResolver) append(p string) error {
+	p = filepath.Join(".", p)
+	current := "."
+	for {
+		parts := strings.SplitN(p, string(filepath.Separator), 2)
+		current = filepath.Join(current, parts[0])
+
+		targets, err := r.readSymlink(current, true)
+		if err != nil {
+			return err
+		}
+
+		p = ""
+		if len(parts) == 2 {
+			p = parts[1]
+		}
+
+		if p == "" || targets != nil {
+			if _, ok := r.resolved[current]; ok {
+				return nil
+			}
+		}
+
+		if targets != nil {
+			r.resolved[current] = struct{}{}
+			for _, target := range targets {
+				if err := r.append(filepath.Join(target, p)); err != nil {
+					return err
+				}
+			}
+			return nil
+		}
+
+		if p == "" {
+			r.resolved[current] = struct{}{}
+			return nil
+		}
+	}
+}
+
+func (r *symlinkResolver) readSymlink(p string, allowWildcard bool) ([]string, error) {
+	realPath := filepath.Join(r.root, p)
+	base := filepath.Base(p)
+	if allowWildcard && containsWildcards(base) {
+		fis, err := ioutil.ReadDir(filepath.Dir(realPath))
+		if err != nil {
+			if os.IsNotExist(err) {
+				return nil, nil
+			}
+			return nil, errors.Wrapf(err, "failed to read dir %s", filepath.Dir(realPath))
+		}
+		var out []string
+		for _, f := range fis {
+			if ok, _ := filepath.Match(base, f.Name()); ok {
+				res, err := r.readSymlink(filepath.Join(filepath.Dir(p), f.Name()), false)
+				if err != nil {
+					return nil, err
+				}
+				out = append(out, res...)
+			}
+		}
+		return out, nil
+	}
+
+	fi, err := os.Lstat(realPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+		return nil, errors.Wrapf(err, "failed to lstat %s", realPath)
+	}
+	if fi.Mode()&os.ModeSymlink == 0 {
+		return nil, nil
+	}
+	link, err := os.Readlink(realPath)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to readlink %s", realPath)
+	}
+	link = filepath.Clean(link)
+	if filepath.IsAbs(link) {
+		return []string{link}, nil
+	}
+	return []string{
+		filepath.Join(string(filepath.Separator), filepath.Join(filepath.Dir(p), link)),
+	}, nil
+}
+
+func containsWildcards(name string) bool {
+	isWindows := runtime.GOOS == "windows"
+	for i := 0; i < len(name); i++ {
+		ch := name[i]
+		if ch == '\\' && !isWindows {
+			i++
+		} else if ch == '*' || ch == '?' || ch == '[' {
+			return true
+		}
+	}
+	return false
+}
+
+// dedupePaths expects input as a sorted list
+func dedupePaths(in []string) []string {
+	out := make([]string, 0, len(in))
+	var last string
+	for _, s := range in {
+		// if one of the paths is root there is no filter
+		if s == "." {
+			return nil
+		}
+		if strings.HasPrefix(s, last+string(filepath.Separator)) {
+			continue
+		}
+		out = append(out, s)
+		last = s
+	}
+	return out
+}