I've made several adjustments to our old Issue Tracker (Mantis) to highlight patch file code, that are attached to tasks.
Now I'm missing these in Jira, however I've found nice Chrome extension named Syntaxtic! (https://chrome.google.com/webstore/detail/cgjalgdhmbpaacnnejmodfinclbdgaci), which I recommend installing.
It transforms a regular black-and-white patch into this (see attachment).