LockFile: Retry lock creation if parent dirs were removed

In the small window between creation of the lock file's parent dirs and
the lock file itself, the parent dirs may be cleaned by an external
process packing refs in the repository. When this scenario occurs, retry
creating the lock file (along with its parent dirs).

Change-Id: Id7ec60c3f7f373b59f1dc8de6b8fa6df6bdf2570
Signed-off-by: Kaushik Lingarkar <quic_kaushikl@quicinc.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/LockFile.java

@@ -24,6 +24,7 @@
 import java.nio.channels.Channels;
 import java.nio.channels.FileChannel;
 import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
 import java.nio.file.StandardCopyOption;
 import java.nio.file.attribute.FileTime;
 import java.text.MessageFormat;
@@ -141,9 +142,8 @@ public boolean lock() throws IOException {
 			throw new IllegalStateException(
 					MessageFormat.format(JGitText.get().lockAlreadyHeld, ref));
 		}
-		FileUtils.mkdirs(lck.getParentFile(), true);
 		try {
-			token = FS.DETECTED.createNewFileAtomic(lck);
+			token = createLockFileWithRetry();
 		} catch (IOException e) {
 			LOG.error(JGitText.get().failedCreateLockFile, lck, e);
 			throw e;
@@ -160,6 +160,19 @@ public boolean lock() throws IOException {
 		return obtainedLock;
 	}
 
+	private FS.LockToken createLockFileWithRetry() throws IOException {
+		try {
+			return createLockFile();
+		} catch (NoSuchFileException e) {
+			return createLockFile();
+		}
+	}
+
+	private FS.LockToken createLockFile() throws IOException {
+		FileUtils.mkdirs(lck.getParentFile(), true);
+		return FS.DETECTED.createNewFileAtomic(lck);
+	}
+
 	/**
 	 * Try to establish the lock for appending.
 	 *