Describe the bug

These four terms are used in the devguide. We should make the terminology uniform, and based on git/GitHub usage.

• I think we should do away with "changeset" completely.
• "Patch" can often be changed to "commit" or "pull request" or even just "change." We have a habit of saying "patch" in the change log: "Patch by Josephine Koder," I'm not sure what to do about that. A few places use the term in the git sense, a diff applied textually, which I think is OK.