Handle tarballs that do not have dir headers

The test asset tarball added by this commit contains the following
entries:
```
dir/file1
dir/file2
dir/nested-dir/file3
```

It explicitly lacks entries for `dir/` and `dir/nested-dir/`. This is
how the `tar` executable generates tarballs when specifying individual
files, and is how the BOSH Director creates the file bundle tarballs
sent to the BOSH agent.

fileutil/tarball_compressor.go

@@ -162,6 +162,11 @@ func (c tarballCompressor) DecompressFileToDir(tarballPath string, dir string, o
 			}
 
 		case tar.TypeReg:
+			directoryPath := filepath.Dir(fullName)
+			if err := c.fs.MkdirAll(directoryPath, fs.FileMode(0755)); err != nil {
+				return bosherr.WrapError(err, "Creating directory for decompressed file")
+			}
+
 			outFile, err := c.fs.OpenFile(fullName, os.O_CREATE|os.O_WRONLY, fs.FileMode(header.Mode))
 			if err != nil {
 				return bosherr.WrapError(err, "Creating decompressed file")

fileutil/tarball_compressor_test.go

@@ -245,6 +245,27 @@ var _ = Describe("tarballCompressor", func() {
 			Expect(err.Error()).To(ContainSubstring(dstDir))
 		})
 
+		It("creates sub-directories even if the tarball does not have a header entry for the directory", func() {
+			compressor := NewTarballCompressor(fs)
+
+			// The contents of this tarball does not contain entries for the dir/ or dir/nested-dir/ directories. The tar executable
+			// automatically creates these directories when extracting files listed under the directories.
+			tarballPath := filepath.Join(fixtureSrcDir(), filepath.FromSlash("../compressor-decompress-missing-directory-header.tgz"))
+			err := compressor.DecompressFileToDir(tarballPath, dstDir, CompressorOptions{})
+			Expect(err).ToNot(HaveOccurred())
+
+			dstElements, err := pathsInDir(dstDir)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(dstElements).To(Equal([]string{
+				"./",
+				"dir/",
+				"dir/file1",
+				"dir/file2",
+				"dir/nested-dir/",
+				"dir/nested-dir/file3",
+			}))
+		})
+
 		Context("with tarball contents owned by root", func() {
 
 			var (