Correct plink -batch option

When GIT_SSH is set to use plink, the correct option name is "-batch"
and not "--batch".  This was a typo introduced when we added support
for plink via GIT_SSH.

Change-Id: I391660e38f5d208bba11e3f2a8f25922de2af878
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

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

@@ -309,7 +309,7 @@ public class TransportGitSsh extends SshTransport implements PackTransport {
 			List<String> args = new ArrayList<String>();
 			args.add(ssh);
 			if (putty)
-				args.add("--batch");
+				args.add("-batch");
 			if (0 < getURI().getPort()) {
 				args.add(putty ? "-P" : "-p");
 				args.add(String.valueOf(getURI().getPort()));