diff`.
When sure that staged changes should be commited to the history, use `git
-commit -m'COMMIT MSG'`.
+commit -m'COMMIT MSG'`. For commit messages, some rules are good to keep in
+mind [1][]:
+- Separate subject from body with a blank line.
+- Limit the subject line to 50 characters.
+- Capitalize the subject line.
+- Do not end the subject line with a period.
+- Use the imperative mood in the subject line.
+- Wrap the body at 72 characters.
+- Use the body to explain what and why vs. how.
+
+[1]: https://chris.beams.io/posts/git-commit/