Fixed CryptoFileSystem

* avoid creation of a file and folder with equal names

main/filesystem-crypto/src/main/java/org/cryptomator/filesystem/crypto/CryptoFile.java

@@ -11,6 +11,9 @@ package org.cryptomator.filesystem.crypto;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import java.util.Optional;
+import java.io.UncheckedIOException;
+import java.nio.file.FileAlreadyExistsException;
+import java.time.Instant;
 
 import org.cryptomator.crypto.engine.Cryptor;
 import org.cryptomator.filesystem.File;
@@ -38,6 +41,9 @@ public class CryptoFile extends CryptoNode implements File {
 
 	@Override
 	public WritableFile openWritable() {
+		if (parent.folder(name).exists()) {
+			throw new UncheckedIOException(new FileAlreadyExistsException(toString()));
+		}
 		return new CryptoWritableFile(cryptor.getFileContentCryptor(), forceGetPhysicalFile().openWritable());
 	}
 

main/filesystem-crypto/src/main/java/org/cryptomator/filesystem/crypto/CryptoFolder.java

@@ -16,6 +16,7 @@ import java.io.Reader;
 import java.io.UncheckedIOException;
 import java.io.Writer;
 import java.nio.channels.Channels;
+import java.nio.file.FileAlreadyExistsException;
 import java.util.Optional;
 import java.util.UUID;
 import java.util.concurrent.atomic.AtomicReference;
@@ -152,6 +153,9 @@ class CryptoFolder extends CryptoNode implements Folder {
 		} else if (!newDirIdGiven) {
 			throw new IllegalStateException("Newly created folder, that didn't exist before, already had an directoryId.");
 		}
+		if (parent.file(name).exists()) {
+			throw new UncheckedIOException(new FileAlreadyExistsException(toString()));
+		}
 		try (Writer writer = Channels.newWriter(dirFile.openWritable(), UTF_8.newEncoder(), -1)) {
 			writer.write(directoryId.get());
 		} catch (IOException e) {