chore(testutil): extract testutil.CreateZip and testutil.CreateTar helpers (#15540)

Extracts `testutil.CreateTar` and `testutil.CreateZip` test helpers.

testutil/archive.go

@@ -0,0 +1,61 @@
+package testutil
+
+import (
+	"archive/tar"
+	"bytes"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/v2/archive"
+)
+
+// Creates an in-memory tar of the files provided.
+// Files in the archive are written with nobody
+// owner/group, and -rw-rw-rw- permissions.
+func CreateTar(t testing.TB, files map[string]string) []byte {
+	var buffer bytes.Buffer
+	writer := tar.NewWriter(&buffer)
+	// Keep track of directories previously added.
+	addedDirs := make(map[string]bool)
+	for path, content := range files {
+		// Add parent directories if they don't exist
+		dir := filepath.Dir(path)
+		if dir != "." && !addedDirs[dir] {
+			err := writer.WriteHeader(&tar.Header{
+				Name:     dir + "/", // Directory names must end with /
+				Mode:     0o755,
+				Typeflag: tar.TypeDir,
+			})
+			require.NoError(t, err)
+			addedDirs[dir] = true
+		}
+
+		err := writer.WriteHeader(&tar.Header{
+			Name: path,
+			Size: int64(len(content)),
+			Uid:  65534, // nobody
+			Gid:  65534, // nogroup
+			Mode: 0o666, // -rw-rw-rw-
+		})
+		require.NoError(t, err)
+
+		_, err = writer.Write([]byte(content))
+		require.NoError(t, err)
+	}
+
+	err := writer.Flush()
+	require.NoError(t, err)
+	return buffer.Bytes()
+}
+
+// Creates an in-memory zip of the files provided.
+// Uses archive.CreateZipFromTar under the hood.
+func CreateZip(t testing.TB, files map[string]string) []byte {
+	ta := CreateTar(t, files)
+	tr := tar.NewReader(bytes.NewReader(ta))
+	za, err := archive.CreateZipFromTar(tr, int64(len(ta)))
+	require.NoError(t, err)
+	return za
+}