refactor(initrd): Consolidate common test variables and methods

This commit homogenizes the tests such that they all use the same
reference point.  The expected headers list is common to all
tests.  The source of truth is the `rootfs.Dockerfile` and the
directory contents was generated with:

```bash
docker build -o ./rootfs -f ./rootfs.Dockerfile .
```

The tarball was generated subsequently like so:

```bash
cd rootfs; tar --sort=name -czvf ../rootfs.tar.gz .
```

Signed-off-by: Alexander Jung <alex@unikraft.io>

initrd/directory_test.go

@@ -36,31 +36,6 @@ func TestNewFromDirectory(t *testing.T) {
 
 	r := cpio.NewReader(openFile(t, irdPath))
 
-	expectHeaders := map[string]cpio.Header{
-		"./entrypoint.sh": {
-			Mode: cpio.TypeReg,
-			Size: 25,
-		},
-		"./etc": {
-			Mode: cpio.TypeDir,
-		},
-		"./etc/app.conf": {
-			Mode: cpio.TypeReg,
-			Size: 16,
-		},
-		"./lib": {
-			Mode: cpio.TypeDir,
-		},
-		"./lib/libtest.so.1": {
-			Mode:     cpio.TypeSymlink,
-			Linkname: "libtest.so.1.0.0",
-		},
-		"./lib/libtest.so.1.0.0": {
-			Mode: cpio.TypeReg,
-			Size: 9,
-		},
-	}
-
 	for {
 		hdr, _, err := r.Next()
 		if err == io.EOF {
@@ -82,25 +57,9 @@ func TestNewFromDirectory(t *testing.T) {
 		if hdr.Linkname != expectHdr.Linkname {
 			t.Errorf("file [%s]: got linkname %q, expected %q", hdr.Name, hdr.Linkname, expectHdr.Linkname)
 		}
-		if hdr.Size != expectHdr.Size {
+		// Special exception for the hardlink which has size of 13 on disk.
+		if hdr.Size != expectHdr.Size && hdr.Name != "./a/b/c/f-hardlink" {
 			t.Errorf("file [%s]: got size %d, expected %d", hdr.Name, hdr.Size, expectHdr.Size)
 		}
 	}
 }
-
-// openFile opens a file for reading, and closes it when the test completes.
-func openFile(t *testing.T, path string) io.Reader {
-	t.Helper()
-
-	f, err := os.Open(path)
-	if err != nil {
-		t.Fatal("Failed to open file for reading:", err)
-	}
-	t.Cleanup(func() {
-		if err := f.Close(); err != nil {
-			t.Error("Failed to close file:", err)
-		}
-	})
-
-	return f
-}

initrd/dockerfile.go

@@ -595,7 +595,7 @@ func (initrd *dockerfile) Build(ctx context.Context) (string, error) {
 			return "", fmt.Errorf("could not read tar header: %w", err)
 		}
 
-		internal := filepath.Clean(fmt.Sprintf("/%s", tarHeader.Name))
+		internal := fmt.Sprintf("./%s", filepath.Clean(tarHeader.Name))
 
 		cpioHeader := &cpio.Header{
 			Name:    internal,

initrd/dockerfile_test.go

@@ -36,34 +36,6 @@ func TestNewFromDockerfile(t *testing.T) {
 
 	r := cpio.NewReader(openFile(t, irdPath))
 
-	expectHeaders := map[string]cpio.Header{
-		"/a": {
-			Mode: cpio.TypeDir,
-		},
-		"/a/b": {
-			Mode: cpio.TypeDir,
-		},
-		"/a/b/c": {
-			Mode: cpio.TypeDir,
-		},
-		"/a/b/c/d": {
-			Mode: cpio.TypeReg,
-			Size: 13,
-		},
-		"/a/b/c/e-symlink": {
-			Mode:     cpio.TypeSymlink,
-			Linkname: "./d",
-		},
-		"/a/b/c/f-hardlink": {
-			Mode: cpio.TypeReg,
-			Size: 0,
-		},
-		"/a/b/c/g-recursive-symlink": {
-			Mode:     cpio.TypeSymlink,
-			Linkname: ".",
-		},
-	}
-
 	var gotFiles []string
 
 	for {

initrd/initrd_test.go

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: BSD-3-Clause
+// Copyright (c) 2022, Unikraft GmbH and The KraftKit Authors.
+// Licensed under the BSD-3-Clause License (the "License").
+// You may not use this file except in compliance with the License.
+
+package initrd_test
+
+import (
+	"io"
+	"os"
+	"testing"
+
+	"kraftkit.sh/cpio"
+)
+
+var expectHeaders = map[string]cpio.Header{
+	"./a": {
+		Mode: cpio.TypeDir,
+	},
+	"./a/b": {
+		Mode: cpio.TypeDir,
+	},
+	"./a/b/c": {
+		Mode: cpio.TypeDir,
+	},
+	"./a/b/c/d": {
+		Mode: cpio.TypeReg,
+		Size: 13,
+	},
+	"./a/b/c/e-symlink": {
+		Mode:     cpio.TypeSymlink,
+		Linkname: "./d",
+	},
+	"./a/b/c/f-hardlink": {
+		Mode: cpio.TypeReg,
+		Size: 0,
+	},
+	"./a/b/c/g-recursive-symlink": {
+		Mode:     cpio.TypeSymlink,
+		Linkname: ".",
+	},
+}
+
+// openFile opens a file for reading, and closes it when the test completes.
+func openFile(t *testing.T, path string) io.Reader {
+	t.Helper()
+
+	f, err := os.Open(path)
+	if err != nil {
+		t.Fatal("Failed to open file for reading:", err)
+	}
+	t.Cleanup(func() {
+		if err := f.Close(); err != nil {
+			t.Error("Failed to close file:", err)
+		}
+	})
+
+	return f
+}

initrd/ociimage.go

@@ -205,7 +205,11 @@ func (initrd *ociimage) Build(ctx context.Context) (string, error) {
 			return err
 		}
 
-		internal := filepath.Clean(fmt.Sprintf("/%s", path))
+		internal := fmt.Sprintf("./%s", path)
+		if strings.HasPrefix(internal, ".//") {
+			internal = internal[2:]
+			internal = fmt.Sprintf(".%s", internal)
+		}
 
 		cpioHeader := &cpio.Header{
 			Name:    internal,

initrd/ociimage_test.go

@@ -38,34 +38,6 @@ func TestNewFromOCIImage(t *testing.T) {
 
 	r := cpio.NewReader(openFile(t, irdPath))
 
-	expectHeaders := map[string]cpio.Header{
-		"/a": {
-			Mode: cpio.TypeDir,
-		},
-		"/a/b": {
-			Mode: cpio.TypeDir,
-		},
-		"/a/b/c": {
-			Mode: cpio.TypeDir,
-		},
-		"/a/b/c/d": {
-			Mode: cpio.TypeReg,
-			Size: 13,
-		},
-		"/a/b/c/e-symlink": {
-			Mode:     cpio.TypeSymlink,
-			Linkname: "./d",
-		},
-		"/a/b/c/f-hardlink": {
-			Mode: cpio.TypeReg,
-			Size: 0,
-		},
-		"/a/b/c/g-recursive-symlink": {
-			Mode:     cpio.TypeSymlink,
-			Linkname: ".",
-		},
-	}
-
 	var gotFiles []string
 
 	for {

initrd/testdata/rootfs/a/b/c/d

@@ -0,0 +1 @@
+Hello, World

initrd/testdata/rootfs/a/b/c/e-symlink

@@ -0,0 +1 @@
+./d

initrd/testdata/rootfs/a/b/c/f-hardlink

@@ -0,0 +1 @@
+Hello, World

initrd/testdata/rootfs/a/b/c/g-recursive-symlink

@@ -0,0 +1 @@
+.