First, ensure you have a Kafka cluster set up and running. You can do this by downloading Kafka from the Apache Kafka website and following the official setup guide. Start the ZooKeeper service and then start the Kafka broker. Verify that the cluster is operational by creating a test topic using Kafka’s command line tools.

Clone the desired GitHub repository to your local machine using the `git clone` command. This will allow you to access the repository's data for further processing. Navigate to the directory where you want to keep the repository and run:
```bash
git clone https://github.com/username/repository.git
```

Identify and extract the data you need from the cloned repository. This could be files, commit history, or any other data stored in the repository. Use Git command line tools or scripts to parse and extract the necessary data. For example, to list all commits, use:
```bash
git log --pretty=format:"%h - %an, %ar : %s"
```

Install a Kafka client library in your preferred programming language to interact with Kafka. If you're using Python, for example, you can use `kafka-python`. Install it using pip:
```bash
pip install kafka-python
```

Develop a script to read the extracted data and produce messages to Kafka. Use the installed Kafka library to create a producer that sends data to a specified Kafka topic. Here’s a basic example in Python:
```python
from kafka import KafkaProducer
producer = KafkaProducer(bootstrap_servers='localhost:9092')

# Example of sending a message
data = "Your data here"
producer.send('your_topic', value=data.encode('utf-8'))
producer.flush()
```

Format the extracted data into a suitable structure for Kafka. This might involve converting data into JSON or another byte-oriented format, ensuring it's ready for consumption by any potential Kafka consumers. Use serialization techniques to prepare your data properly.

Execute your Kafka producer script and monitor its operation. Ensure that messages are being successfully sent to the Kafka topic. Use Kafka’s command line tools to verify that the messages are appearing on the topic:
```bash
kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic your_topic --from-beginning
```

By following these steps, you can effectively move data from a GitHub repository to a Kafka cluster without relying on third-party connectors or integrations.