javagit/src/main/java/edu/nyu/cs/javagit/client/cli/CliGitCheckout.java
private void checkRefAgainstRefType(Ref ref, RefType refType) {
        if (ref != null && ref.getRefType() == refType) {
            throw new IllegalArgumentException("Invalid ref type passed as argument to checkout");
        }
    }
private void checkRefAgainstRefType(Ref ref, RefType refType) {
        if (ref != null && ref.getRefType() == refType) {
            throw new IllegalArgumentException("Invalid ref type passed as argument to checkout");
        }
    }
This is just a test method for verifying that a given ref is not of refType provided as one of the parameters.

@param ref     This could be branch, sha1 etc.
@param refType This is the <code>RefType</code> which the ref should not match.