RevWalkTextBuiltin: Add -n to limit number of commits returned

Implementing the -<#> flag from C git is less trivial.

Change-Id: Idb55a303304a6d4055aaf37d0b4dcf92c684e25f

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

@@ -146,6 +146,9 @@ abstract class RevWalkTextBuiltin extends TextBuiltin {
 		revLimiter.add(MessageRevFilter.create(msg));
 	}
 
+	@Option(name = "--max-count", aliases = "-n", metaVar = "metaVar_n")
+	private int maxCount = -1;
+
 	@Override
 	protected void run() throws Exception {
 		walk = createWalk();
@@ -218,7 +221,8 @@ abstract class RevWalkTextBuiltin extends TextBuiltin {
 	protected int walkLoop() throws Exception {
 		int n = 0;
 		for (final RevCommit c : walk) {
-			n++;
+			if (++n > maxCount && maxCount >= 0)
+				break;
 			show(c);
 		}
 		if (walk instanceof ObjectWalk) {