test: add basic integration tests

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/github.com/moby/buildkit/util/testutil/tar.go

@@ -0,0 +1,50 @@
+package testutil
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"io"
+
+	"github.com/pkg/errors"
+)
+
+type TarItem struct {
+	Header *tar.Header
+	Data   []byte
+}
+
+func ReadTarToMap(dt []byte, compressed bool) (map[string]*TarItem, error) {
+	m := map[string]*TarItem{}
+	var r io.Reader = bytes.NewBuffer(dt)
+	if compressed {
+		gz, err := gzip.NewReader(r)
+		if err != nil {
+			return nil, errors.Wrapf(err, "error creating gzip reader")
+		}
+		defer gz.Close()
+		r = gz
+	}
+	tr := tar.NewReader(r)
+	for {
+		h, err := tr.Next()
+		if err != nil {
+			if err == io.EOF {
+				return m, nil
+			}
+			return nil, errors.Wrap(err, "error reading tar")
+		}
+		if _, ok := m[h.Name]; ok {
+			return nil, errors.Errorf("duplicate entries for %s", h.Name)
+		}
+
+		var dt []byte
+		if h.Typeflag == tar.TypeReg {
+			dt, err = io.ReadAll(tr)
+			if err != nil {
+				return nil, errors.Wrapf(err, "error reading file")
+			}
+		}
+		m[h.Name] = &TarItem{Header: h, Data: dt}
+	}
+}