[findBugs] Prevent potential NPE in CloneCommand.init()

File.listFiles() returns null if the File is not a directory, improve
validation of directory and gitDir to fix this.

Change-Id: I763d08835faf96a0beb8e706992df0908526bd2c
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -314,6 +314,8 @@ indexFileIsTooLargeForJgit=Index file is too large for jgit
 indexSignatureIsInvalid=Index signature is invalid: {0}
 indexWriteException=Modified index could not be written
 initFailedBareRepoDifferentDirs=When initializing a bare repo with directory {0} and separate git-dir {1} specified both folders must point to the same location
+initFailedDirIsNoDirectory=Cannot set directory to ''{0}'' which is not a directory
+initFailedGitDirIsNoDirectory=Cannot set git-dir to ''{0}'' which is not a directory
 initFailedNonBareRepoSameDirs=When initializing a non-bare repo with directory {0} and separate git-dir {1} specified both folders should not point to the same location
 inMemoryBufferLimitExceeded=In-memory buffer limit exceeded
 inputDidntMatchLength=Input did not match supplied length. {0} bytes are missing.

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

@@ -155,6 +155,7 @@ public class CloneCommand extends TransportCommand<CloneCommand, Git> {
 		command.setBare(bare);
 		if (directory == null && gitDir == null)
 			directory = new File(u.getHumanishName(), Constants.DOT_GIT);
+		validateDirs(directory, gitDir, bare);
 		if (directory != null && directory.exists()
 				&& directory.listFiles().length != 0)
 			throw new JGitInternalException(MessageFormat.format(
@@ -511,6 +512,15 @@ public class CloneCommand extends TransportCommand<CloneCommand, Git> {
 	private static void validateDirs(File directory, File gitDir, boolean bare)
 			throws IllegalStateException {
 		if (directory != null) {
+			if (directory.exists() && !directory.isDirectory()) {
+				throw new IllegalStateException(MessageFormat.format(
+						JGitText.get().initFailedDirIsNoDirectory, directory));
+			}
+			if (gitDir != null && gitDir.exists() && !gitDir.isDirectory()) {
+				throw new IllegalStateException(MessageFormat.format(
+						JGitText.get().initFailedGitDirIsNoDirectory,
+						gitDir));
+			}
 			if (bare) {
 				if (gitDir != null && !gitDir.equals(directory))
 					throw new IllegalStateException(MessageFormat.format(

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -373,6 +373,8 @@ public class JGitText extends TranslationBundle {
 	/***/ public String indexSignatureIsInvalid;
 	/***/ public String indexWriteException;
 	/***/ public String initFailedBareRepoDifferentDirs;
+	/***/ public String initFailedDirIsNoDirectory;
+	/***/ public String initFailedGitDirIsNoDirectory;
 	/***/ public String initFailedNonBareRepoSameDirs;
 	/***/ public String inMemoryBufferLimitExceeded;
 	/***/ public String inputDidntMatchLength;