Fix "reset -hard" bug that folders could not be created

Creating a folder failed in case a file with the same name already
existed.

Bug: 479266
Change-Id: Ia987660ec0968ad4081dbd5a60e80660539497e3
Signed-off-by: René Scheibe <rene.scheibe@gmail.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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

@@ -189,6 +189,22 @@ public class ResetCommandTest extends RepositoryTestCase {
 		assertFalse(new File(db.getWorkTree(), "dir-or-file").exists());
 	}
 
+	@Test
+	public void testHardResetWithConflicts_CreateFolder_UnstagedChanges() throws Exception {
+		setupRepository();
+
+		writeTrashFile("dir-or-file/c.txt", "content");
+		git.add().addFilepattern("dir-or-file/c.txt").call();
+		git.commit().setMessage("adding dir-or-file/c.txt").call();
+
+		FileUtils.delete(new File(db.getWorkTree(), "dir-or-file"), FileUtils.RECURSIVE);
+		writeTrashFile("dir-or-file", "content");
+
+		// bug 479266: cannot create folder "dir-or-file"
+		git.reset().setMode(ResetType.HARD).setRef(Constants.HEAD).call();
+		assertTrue(new File(db.getWorkTree(), "dir-or-file/c.txt").exists());
+	}
+
 	@Test
 	public void testResetToNonexistingHEAD() throws JGitInternalException,
 			AmbiguousObjectException, IOException, GitAPIException {

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/DirCacheCheckoutTest.java

@@ -1977,6 +1977,29 @@ public class DirCacheCheckoutTest extends RepositoryTestCase {
 		}
 	}
 
+	@Test
+	public void testCheckoutWithEmptyIndexDoesntOverwrite() throws Exception {
+		try (Git git = new Git(db);
+				TestRepository<Repository> db_t = new TestRepository<>(db)) {
+			// prepare the commits
+			BranchBuilder master = db_t.branch("master");
+			RevCommit mergeCommit = master.commit()
+					.add("p/x", "headContent")
+					.message("m0").create();
+			master.commit().add("p/x", "headContent").message("m1").create();
+			git.checkout().setName("master").call();
+
+			// empty index and write unsaved data in 'p'
+			git.rm().addFilepattern("p").call();
+			writeTrashFile("p", "important data");
+
+			git.checkout().setName(mergeCommit.getName()).call();
+
+			assertEquals("", indexState(CONTENT));
+			assertEquals("important data", read("p"));
+		}
+	}
+
 	private static class TestFileTreeIterator extends FileTreeIterator {
 
 		// For assertions only

org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java

@@ -1470,6 +1470,9 @@ public class DirCacheCheckout {
 		ObjectLoader ol = or.open(entry.getObjectId());
 		File f = new File(repo.getWorkTree(), entry.getPathString());
 		File parentDir = f.getParentFile();
+		if (parentDir.isFile()) {
+			FileUtils.delete(parentDir);
+		}
 		FileUtils.mkdirs(parentDir, true);
 		FS fs = repo.getFS();
 		WorkingTreeOptions opt = repo.getConfig().get(WorkingTreeOptions.KEY);