How can I create a patch using Git?
Every Drupal.org project has a tab title 'Version control', click on it and it will take you to a page with Git instructions, including a section titled 'Creating a patch'.

See here for an example: http://drupal.org/project/wysiwyg_fields/git-instructions

Code below is copied from the D.o. instructions.

git checkout -b [description]-[issue-number]


Make your changes. Note the change in syntax for issue-related commit messages. See the Commit messages page for details.

git add -A
git commit -m "Issue #[issue number] by [comma-separated usernames]: [Short summary of the change]."


Roll the patch.

git status
git fetch origin
git rebase origin/6.x-1.x
git format-patch origin/6.x-1.x --stdout &gt; [description]-[issue-number]-[comment-number].patch