archive: Release resources before returning

The only caller exits immediately after calling execute() so this
shouldn't make a difference, but it's good practice and should make it
easier to expose the functionality in a public API later.

Change-Id: Ia6cd2ce8382f1a62e576409107fc5c9a6b321fb6

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Archive.java

@@ -78,15 +78,17 @@ class Archive extends TextBuiltin {
 
 	@Override
 	protected void run() throws Exception {
-		final TreeWalk walk = new TreeWalk(db);
-		final ObjectReader reader = walk.getObjectReader();
 		final MutableObjectId idBuf = new MutableObjectId();
 		final Archiver fmt = formats.get(format);
-		final ArchiveOutputStream outa = fmt.createArchiveOutputStream(outs);
 
 		if (tree == null)
 			throw die(CLIText.get().treeIsRequired);
 
+		final ArchiveOutputStream outa = fmt.createArchiveOutputStream(outs);
+		final TreeWalk walk = new TreeWalk(db);
+		final ObjectReader reader = walk.getObjectReader();
+
+		try {
 			walk.reset();
 			walk.addTree(tree);
 			walk.setRecursive(true);
@@ -102,9 +104,11 @@ class Archive extends TextBuiltin {
 				walk.getObjectId(idBuf, 0);
 				fmt.putEntry(name, mode, reader.open(idBuf), outa);
 			}
-
+		} finally {
+			reader.release();
 			outa.close();
 		}
+	}
 
 	static private void warnArchiveEntryModeIgnored(String name) {
 		System.err.println(MessageFormat.format( //