[From an email by Eric Evans. Cleanup welcome.]
I know there are at least a few people that use Git to work up patches for Cassandra and so I thought I'd draw your attention to the excellent git-jira-attacher.py script by David Reisss. This script turns a range of commits into a patch series and attaches them to Jira. See CASSANDRA-139 for an example of what this looks like.
I also have a fork of David's repo with a couple of additional scripts, jira-apply and jira-am.
jira-apply is useful with or without Git for applying patches that may or may not have been created with Git, think of it as a Jira enabled version of patch(1).
jira-am is what you would use to apply a patch series that was created by git-format-patch/git-jira-attacher.py, and attached to a Jira incident. It will apply the attachments in order, creating a new Git changeset for each patch in the series. Think of jira-am as a Jira enabled version of git-am(1).
Comments, questions, suggestions, complaints, patches, etc regarding the scripts in my repo welcome.