mz843: generate integration tar fixtures on the fly

.gitignore

@@ -5,4 +5,9 @@ BUILD.bazel
 .idea/**
 *.iml
 .vagrant
-.vscode/
+.vscode/
+# Generated by integration TestMain (generateTarFixtures), never commit binary archives
+integration/context/tars/file.tar
+integration/context/tars/file.tar.gz
+integration/context/tars/file.bz2
+integration/context/tars/sys.tar.gz

integration/fixtures.go

@@ -0,0 +1,167 @@
+/*
+Copyright 2026 OSS Container Tools
+
+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 integration
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"time"
+)
+
+var fixtureModTime = time.Unix(1600000000, 0)
+
+type tarEntry struct {
+	name     string
+	typeflag byte
+	mode     int64
+	content  string
+}
+
+func buildTar(entries []tarEntry) ([]byte, error) {
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	for _, e := range entries {
+		hdr := &tar.Header{
+			Name:     e.name,
+			Typeflag: e.typeflag,
+			Mode:     e.mode,
+			ModTime:  fixtureModTime,
+		}
+		if e.typeflag == tar.TypeReg {
+			hdr.Size = int64(len(e.content))
+		}
+		err := tw.WriteHeader(hdr)
+		if err != nil {
+			return nil, err
+		}
+		if e.typeflag == tar.TypeReg {
+			_, err = tw.Write([]byte(e.content))
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+	err := tw.Close()
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+func gzipBytes(in []byte) ([]byte, error) {
+	var buf bytes.Buffer
+	zw := gzip.NewWriter(&buf)
+	_, err := zw.Write(in)
+	if err != nil {
+		return nil, err
+	}
+	err = zw.Close()
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+// bzip2Bytes shells out to bzip2 because the standard library has no bzip2 writer.
+func bzip2Bytes(in []byte) ([]byte, error) {
+	cmd := exec.Command("bzip2", "-c")
+	cmd.Stdin = bytes.NewReader(in)
+	var out bytes.Buffer
+	cmd.Stdout = &out
+	err := cmd.Run()
+	if err != nil {
+		return nil, fmt.Errorf("bzip2: %w", err)
+	}
+	return out.Bytes(), nil
+}
+
+// generateTarFixtures writes the tar archives consumed by the ADD integration
+// tests into context/tars, so the repository holds no committed binary archives.
+func generateTarFixtures() error {
+	_, ex, _, _ := runtime.Caller(0)
+	dir := filepath.Join(filepath.Dir(ex), "context", "tars")
+	err := os.MkdirAll(dir, 0o755)
+	if err != nil {
+		return err
+	}
+
+	plain, err := buildTar([]tarEntry{
+		{name: "./", typeflag: tar.TypeDir, mode: 0o755},
+		{name: "./uncompressedFile", typeflag: tar.TypeReg, mode: 0o644},
+	})
+	if err != nil {
+		return err
+	}
+
+	gzipped, err := buildTar([]tarEntry{
+		{name: "./", typeflag: tar.TypeDir, mode: 0o755},
+		{name: "./compressedFile", typeflag: tar.TypeReg, mode: 0o644, content: "compressed\n"},
+	})
+	if err != nil {
+		return err
+	}
+
+	bzipped, err := buildTar([]tarEntry{
+		{name: "./", typeflag: tar.TypeDir, mode: 0o755},
+		{name: "./bzCompressedFile", typeflag: tar.TypeReg, mode: 0o644, content: "bzip\n"},
+	})
+	if err != nil {
+		return err
+	}
+
+	sys, err := buildTar([]tarEntry{
+		{name: "sys/", typeflag: tar.TypeDir, mode: 0o755},
+		{name: "sys/fs/", typeflag: tar.TypeDir, mode: 0o755},
+		{name: "sys/fs/foo", typeflag: tar.TypeReg, mode: 0o644},
+	})
+	if err != nil {
+		return err
+	}
+
+	gzippedGz, err := gzipBytes(gzipped)
+	if err != nil {
+		return err
+	}
+	sysGz, err := gzipBytes(sys)
+	if err != nil {
+		return err
+	}
+	bzippedBz, err := bzip2Bytes(bzipped)
+	if err != nil {
+		return err
+	}
+
+	fixtures := map[string][]byte{
+		"file.tar":    plain,
+		"file.tar.gz": gzippedGz,
+		"file.bz2":    bzippedBz,
+		"sys.tar.gz":  sysGz,
+	}
+	for name, data := range fixtures {
+		err = os.WriteFile(filepath.Join(dir, name), data, 0o644)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

integration/integration_test.go

@@ -121,6 +121,10 @@ func TestMain(m *testing.M) {
 	}
 
 	config = initIntegrationTestConfig()
+	if err = generateTarFixtures(); err != nil {
+		fmt.Println("Couldn't generate tar fixtures", err)
+		os.Exit(1)
+	}
 	if allDockerfiles, err = FindDockerFiles(dockerfilesPath, config.dockerfilesPattern); err != nil {
 		fmt.Println("Coudn't create map of dockerfiles", err)
 		os.Exit(1)