MINOR: Contribution guidelines for developers (#1164)

* MINOR: Contribution guidelines for developers

* MINOR: Update README.md to include link to contribution guidelines

CONTRIBUTING.md

@@ -0,0 +1,188 @@
+# Contributing
+
+In order for us to consider merging a contribution, you will need to sign our
+**C**ontributor **L**icense **A**greement.
+
+> The purpose of a CLA is to ensure that the guardian of a project's outputs has the necessary ownership or grants of rights over all contributions to allow them to distribute under the chosen licence.
+> [Wikipedia](http://en.wikipedia.org/wiki/Contributor_License_Agreement)
+
+You can read and sign our full Contributor License Agreement [here](http://clabot.confluent.io/cla).
+
+## Reporting Bugs and Issues
+
+Report bugs and issues by creating a new GitHub issue. Prior to creating an issue, please search
+through existing issues so that you are not creating duplicate ones. If a pull request exists that
+corresponds to the issue, mention this pull request on the GitHub issue.
+
+## Guidelines for Contributing Code, Examples, Documentation
+
+Code changes are submitted via a pull request (PR). When submitting a PR use the following
+guidelines:
+
+* Follow the style guide below
+* Add/update documentation appropriately for the change you are making.
+* Non-trivial changes should include unit tests covering the new functionality and potentially integration tests.
+* Bug fixes should include unit tests and/or integration tests proving the issue is fixed.
+* Try to keep pull requests short and submit separate ones for unrelated features.
+* Keep formatting changes in separate commits to make code reviews easier and distinguish them from actual code changes.
+
+### Code Style
+This connector is using a coding style that generally follows the [Google Java coding standard guide](https://google.github.io/styleguide/javaguide.html).
+
+Some conventions worth mentioning are:
+
+* Indentation (single tab) is 2 spaces.
+* All import statements are listed explicitly. The wildcard (*) is not used in imports.
+* Imports are groups as follows:
+```
+    import all packages not listed below (all other imports)
+    <blank line>
+    import all javax.* packages
+    import all java.* packages
+    <blank line>
+    import all io.confluent.* packages
+    <blank line>
+    import static packages
+```
+* Javadoc is highly recommended and often required during reviews in interfaces and public or protected classes and methods.
+
+### Titles and changelogs
+
+The title of a pull request is used as an entry on the release notes (aka changelogs) of the
+connector in every release.
+
+For this reason, please use a brief but descriptive title for your pull request. If GitHub shortens
+your pull request title when you issue the pull request adding the excessive part to the pull
+request description, make sure that you correct the title before or after you issue the pull
+request.
+
+If the fix is a minor fix you are encouraged to use the tag `MINOR:` followed by your pull request
+title. You may link the corresponding issue to the description of your pull request but adding it to
+the title will not be useful during changelog generation.
+
+When reverting a previous commit, use the prefix `Revert ` on the pull request title (automatically
+added by GitHub when a pull request is created to revert an existing commit).
+
+### Tests
+Every pull request should contain a sufficient amount of tests that assess your suggested code
+changes. It’s highly recommended that you also check the code coverage of the production code you
+are adding to make sure that your changes are covered sufficiently by the test code.
+
+### Description
+Including a good description when you issue your pull requests helps significantly with reviews.
+Feel free to follow the template that is when issuing a pull request and mention how your changes
+are tested.
+
+### Backporting Commits
+If your code changes are essentially bug fixes that make sense to backport to existing releases make sure to target the earliest release branch (e.g. 2.0.x) that should contain your changes. When selecting the release branch you should also consider how easy it will be to resolve any conflicts in newer release branches, including the `master` branch.
+
+## Github Workflow
+
+1. Fork the connector repository into your GitHub account: https://github.com/confluentinc/kafka-connect-jdbc/fork
+
+2. Clone your fork of the GitHub repository, replacing `<username>` with your GitHub username.
+
+    Use ssh (recommended):
+
+    ```bash
+    git clone [email protected]:<username>/kafka-connect-jdbc.git
+    ```
+
+    Or https:
+
+    ```bash
+    git clone https://github.com/<username>/kafka-connect-jdbc.git
+    ```
+
+3. Add a remote to keep up with upstream changes.
+
+    ```bash
+    git remote add upstream https://github.com/confluentinc/kafka-connect-jdbc.git
+    ```
+
+    If you already have a copy, fetch upstream changes.
+
+    ```bash
+    git fetch upstream
+    ```
+
+    or
+
+    ```bash
+    git remote update
+    ```
+
+4. Create a feature branch to work in.
+
+    ```bash
+    git checkout -b feature-xyz upstream/master
+    ```
+
+5. Work in your feature branch.
+
+    ```bash
+    git commit -a --verbose
+    ```
+
+6. Periodically rebase your changes
+
+    ```bash
+    git pull --rebase
+    ```
+
+7. When done, combine ("squash") related commits into a single one
+
+    ```bash
+    git rebase -i upstream/master
+    ```
+
+    This will open your editor and allow you to re-order commits and merge them:
+    - Re-order the lines to change commit order (to the extent possible without creating conflicts)
+    - Prefix commits using `s` (squash) or `f` (fixup) to merge extraneous commits.
+
+8. Submit a pull-request
+
+    ```bash
+    git push origin feature-xyz
+    ```
+
+    Go to your fork main page
+
+    ```bash
+    https://github.com/<username>/kafka-connect-jdbc.git
+    ```
+
+    If you recently pushed your changes GitHub will automatically pop up a `Compare & pull request`
+    button for any branches you recently pushed to. If you click that button it will automatically
+    offer you to submit your pull-request to the `confluentinc` connector repository.
+
+    - Give your pull-request a meaningful title as described [above](#titles-and-changelogs).
+    - In the description, explain your changes and the problem they are solving.
+
+9. Addressing code review comments
+
+    Repeat steps 5. through 7. to address any code review comments and rebase your changes if necessary.
+
+    Push your updated changes to update the pull request
+
+    ```bash
+    git push origin [--force] feature-xyz
+    ```
+
+    `--force` may be necessary to overwrite your existing pull request in case your
+    commit history was changed when performing the rebase.
+
+    Note: Be careful when using `--force` since you may lose data if you are not careful.
+
+    ```bash
+    git push origin --force feature-xyz
+    ```
+
+## Useful Resources for Developers
+
+1. Connector Developer Guide: https://docs.confluent.io/platform/current/connect/devguide.html
+2. A Guide to the Confluent Verified Integrations Program: https://www.confluent.io/blog/guide-to-confluent-verified-integrations-program/
+3. Verification Guide for Confluent Platform Integrations: https://cdn.confluent.io/wp-content/uploads/Verification-Guide-Confluent-Platform-Connectors-Integrations.pdf
+4. From Zero to Hero with Kafka Connect: https://www.confluent.io/kafka-summit-lon19/from-zero-to-hero-with-kafka-connect/
+5. 4 Steps to Creating Apache Kafka Connectors with the Kafka Connect API: https://www.confluent.io/blog/create-dynamic-kafka-connect-source-connectors/
+6. How to Write a Connector for Kafka Connect – Deep Dive into Configuration Handling: https://www.confluent.io/blog/write-a-kafka-connect-connector-with-configuration-handling/

README.md

@@ -23,6 +23,7 @@ Contributions can only be accepted if they contain appropriate testing. For exam
 
 - Source Code: https://github.com/confluentinc/kafka-connect-jdbc
 - Issue Tracker: https://github.com/confluentinc/kafka-connect-jdbc/issues
+- Learn how to work with the connector's source code by reading our [Development and Contribution guidelines](CONTRIBUTING.md).
 
 # Information