ant: Open Repository and Git in try-with-resource

To prevent potential resource leak.

Change-Id: I3f4af9037c9d26ec575b529ab66066365ab918a5
Signed-off-by: David Pursehouse <david.pursehouse@sonymobile.com>

org.eclipse.jgit.ant/src/org/eclipse/jgit/ant/tasks/GitAddTask.java

 		}
 
 		AddCommand gitAdd;
-		try {
-			Repository repo = new FileRepositoryBuilder().readEnvironment()
-					.findGitDir(src).build();
-			gitAdd = new Git(repo).add();
+		try (Repository repo = new FileRepositoryBuilder().readEnvironment()
+				.findGitDir(src).build();
+			Git git = new Git(repo);) {
+			gitAdd = git.add();
 		} catch (IOException e) {
 			throw new BuildException("Could not access repository " + src, e);
 		}

org.eclipse.jgit.ant/src/org/eclipse/jgit/ant/tasks/GitCheckoutTask.java

 	@Override
 	public void execute() throws BuildException {
 		CheckoutCommand checkout;
-		try {
-			Repository repo = new FileRepositoryBuilder().readEnvironment()
-					.findGitDir(src).build();
-			checkout = new Git(repo).checkout();
+		try (Repository repo = new FileRepositoryBuilder().readEnvironment()
+				.findGitDir(src).build();
+			Git git = new Git(repo)) {
+			checkout = git.checkout();
 		} catch (IOException e) {
 			throw new BuildException("Could not access repository " + src, e);
 		}