Fix an invalid format string

The %x format specifier is not valid for a byte array.
This patch fixes a bug that would cause an IllegalFormatConversionException.

Change-Id: I025975eca7b2f10bbafa39f5519f8668e6536541
Signed-off-by: David Pletcher <dpletcher@google.com>

org.eclipse.jgit/src/org/eclipse/jgit/transport/HMACSHA1NonceGenerator.java

@@ -99,9 +99,7 @@ public class HMACSHA1NonceGenerator implements NonceGenerator {
 		} catch (UnsupportedEncodingException e) {
 			throw new IllegalStateException(e);
 		}
-		String sentNonce = String.format(
-				"%d-%20X", new Long(timestamp), rawHmac); //$NON-NLS-1$
-		return sentNonce;
+		return Long.toString(timestamp) + "-" + toHex(rawHmac); //$NON-NLS-1$
 	}
 
 	@Override
@@ -146,4 +144,15 @@ public class HMACSHA1NonceGenerator implements NonceGenerator {
 			return NonceStatus.SLOP;
 		}
 	}
+
+	private static final String HEX = "0123456789ABCDEF"; //$NON-NLS-1$
+
+	private static String toHex(byte[] bytes) {
+		StringBuilder builder = new StringBuilder(2 * bytes.length);
+		for (byte b : bytes) {
+			builder.append(HEX.charAt((b & 0xF0) >> 4));
+			builder.append(HEX.charAt(b & 0xF));
+		}
+		return builder.toString();
+	}
 }