If you were actually editing a patch file, that would be a concern; but in Git, you only edit one hunk at a time, so all’s fine as long as you don‘t mess up the context lines—Git will ignore the source and destination line numbers and counts that your editing has likely rendered incorrect. (An easy way to mess up the context lines is to have your editor strip trailing whitespace on save, as the unified diff syntax for an empty context line is a single space. If anybody asks, in no way did this cause me to be puzzled for literal weeks by hunk edits failing seemingly at random.)