Fix ChainingCredentialsProvider

The ChainingCredentialsProvider gave up chaining to the next provider if
the first one returned no credentials items for the given URI.

Change-Id: I9539c50db35e564db9d43d8ebb71d7e9c6fdcc19
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/transport/ChainingCredentialsProvider.java

@@ -113,9 +113,15 @@ public class ChainingCredentialsProvider extends CredentialsProvider {
 			throws UnsupportedCredentialItem {
 		for (CredentialsProvider p : credentialProviders) {
 			if (p.supports(items)) {
-				p.get(uri, items);
+				if (!p.get(uri, items)) {
-				if (isAnyNull(items))
+					if (p.isInteractive()) {
+						return false; // user cancelled the request
+					}
 					continue;
+				}
+				if (isAnyNull(items)) {
+					continue;
+				}
 				return true;
 			}
 		}