Added very small optimization to exact rename detection

Optimized a small loop in findExactRenames. The loop would go through
all the items in a list of DiffEntries even after it already found
what it was looking for. I made it break out of the loop as soon as
a good match was found.

Change-Id: I28741e0c49ce52d8008930a87cd1db7037700a61

org.eclipse.jgit/src/org/eclipse/jgit/diff/RenameDetector.java

@@ -351,8 +351,10 @@ public class RenameDetector {
 				List<DiffEntry> list = (List<DiffEntry>) del;
 				DiffEntry best = null;
 				for (DiffEntry e : list) {
-					if (best == null && sameType(e.oldMode, dst.newMode))
+					if (sameType(e.oldMode, dst.newMode)) {
 						best = e;
+						break;
+					}
 				}
 				if (best != null) {
 					if (best.changeType == ChangeType.DELETE) {