Create parent dir if necessary on checkout

An example where this is necessary is when a whole directory was deleted
and checkout is used to restore a file which was in that directory.

Bug: 372133
Change-Id: I1d45e0a5d2525fe1fdfbf08c9c5c166dd909e9fd
Signed-off-by: Robin Stocker <robin@nibor.org>

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/CheckoutCommandTest.java

@@ -219,6 +219,21 @@ public class CheckoutCommandTest extends RepositoryTestCase {
 				indexState(db2, CONTENT));
 	}
 
+	@Test
+	public void testCheckoutOfFileWithInexistentParentDir() throws Exception {
+		File a = writeTrashFile("dir/a.txt", "A");
+		writeTrashFile("dir/b.txt", "A");
+		git.add().addFilepattern("dir/a.txt").addFilepattern("dir/b.txt")
+				.call();
+		git.commit().setMessage("Added dir").call();
+
+		File dir = new File(db.getWorkTree(), "dir");
+		FileUtils.delete(dir, FileUtils.RECURSIVE);
+
+		git.checkout().addPath("dir/a.txt").call();
+		assertTrue(a.exists());
+	}
+
 	@Test
 	public void testDetachedHeadOnCheckout() throws JGitInternalException,
 			IOException, GitAPIException {

org.eclipse.jgit/src/org/eclipse/jgit/api/CheckoutCommand.java

@@ -78,6 +78,7 @@ import org.eclipse.jgit.revwalk.RevTree;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.treewalk.TreeWalk;
 import org.eclipse.jgit.treewalk.filter.PathFilterGroup;
+import org.eclipse.jgit.util.FileUtils;
 
 /**
  * Checkout a branch to the working tree
@@ -297,9 +298,11 @@ public class CheckoutCommand extends GitCommand<Ref> {
 						public void apply(DirCacheEntry ent) {
 							ent.setObjectId(blobId);
 							ent.setFileMode(mode);
+							File file = new File(workTree, ent.getPathString());
+							File parentDir = file.getParentFile();
 							try {
-								DirCacheCheckout.checkoutEntry(repo, new File(
-										workTree, ent.getPathString()), ent, r);
+								FileUtils.mkdirs(parentDir, true);
+								DirCacheCheckout.checkoutEntry(repo, file, ent, r);
 							} catch (IOException e) {
 								throw new JGitInternalException(
 										MessageFormat.format(