cred: add a free function wrapper

include/git2/transport.h

@@ -307,6 +307,17 @@ GIT_EXTERN(int) git_cred_ssh_key_memory_new(
 	const char *privatekey,
 	const char *passphrase);
 
+
+/**
+ * Free a credential.
+ *
+ * This is only necessary if you own the object; that is, if you are a
+ * transport.
+ *
+ * @param cred the object to free
+ */
+GIT_EXTERN(void) git_cred_free(git_cred *cred);
+
 /**
  * Signature of a function which acquires a credential object.
  *

src/transports/cred.c

@@ -378,3 +378,11 @@ int git_cred_username_new(git_cred **cred, const char *username)
 	*cred = (git_cred *) c;
 	return 0;
 }
+
+void git_cred_free(git_cred *cred)
+{
+	if (!cred)
+		return;
+
+	cred->free(cred);
+}