Adds a "Copy Diff" button to the PR nav that copies the unified diff to the clipboard
// ==UserScript==
// @name GitHub PR Copy Diff
// @namespace http://tampermonkey.net/
// @icon https://github.githubassets.com/favicons/favicon-dark.png
// @version 2026.06.19
// @description Adds a "Copy Diff" button to the PR nav that copies the unified diff to the clipboard
// @author KakkoiDev
// @match https://github.com/*
// @grant GM_xmlhttpRequest
// @grant GM_setClipboard
// @connect github.com
// @connect githubusercontent.com
// @license MIT
// ==/UserScript==
// Broad @match needed: GitHub uses SPA navigation, so the MutationObserver
// re-adds the button as the PR header re-renders.
//
// GM_xmlhttpRequest + GM_setClipboard (not fetch + navigator.clipboard):
// github.com/<o>/<r>/pull/<n>.diff 302-redirects cross-origin to
// patch-diff.githubusercontent.com with no CORS header, so a page fetch is
// blocked. GM_xmlhttpRequest bypasses CORS and sends cookies (private PRs).
(function() {
'use strict';
// === OPEN BUG + DIAGNOSTICS - do NOT commit/release to Greasy Fork as-is (logs to every user's console) ===
// Symptom (reported 2026-06-18): the "Copy Diff" button vanishes when GitHub re-renders the PR
// header (e.g. switching tabs) and does not come back.
// Status: NOT reproduced yet. Single instance self-heals - the log shows the button briefly removed
// on the first re-render then re-added (INSERTED, btns=1, visible=1) and stable across /changes,
// /commits, /checks, /pull/N. The earlier "two copies fighting (GF install + dev loader)" guess
// was WRONG - user confirmed only one instance was running.
// Still open: some re-render / scroll (sticky header?) / browser-tab-switch path leaves it gone.
// This logging stays ON in the dev loader to capture the next occurrence. Read the [copy-diff] lines
// around the moment it disappears:
// "skip: no filesTab" -> the Files-tab selector stopped matching the new header
// "skip: btn already exists" + visible=0 -> button detached/hidden, but the GLOBAL getElementById
// guard blocks re-adding it to the visible nav (lead suspect)
// btns 1 -> 0 with no following INSERTED -> the observer/re-add never fired for that mutation
// filesTabs=2 -> a second (sticky?) tab nav exists; button is in the wrong one
// Likely fix once confirmed: drop the global getElementById guard; keep a button adjacent to the
// CURRENTLY VISIBLE Files tab and remove any stray/detached copies.
const DEBUG = true;
let _dbgLast = '';
function dbg(action) {
if (!DEBUG) return;
const filesTabs = document.querySelectorAll('#prs-files-anchor-tab, a[href*="/pull/"][href$="/files"]').length;
const all = [...document.querySelectorAll('#gh-copy-diff-btn')];
const sig = `${action} | path=${location.pathname} filesTabs=${filesTabs} btns=${all.length} visible=${all.filter((b) => b.offsetParent !== null).length}`;
if (sig === _dbgLast) return; // the observer fires constantly; only log when the state changes
_dbgLast = sig;
console.log('[copy-diff]', sig);
}
// === END TEMP DEBUG ===
function getPrInfo() {
const m = location.pathname.match(/^\/([^/]+)\/([^/]+)\/pull\/(\d+)/);
if (!m) return null;
return { owner: m[1], repo: m[2], number: m[3] };
}
function flash(btn, msg) {
btn.textContent = msg;
btn.disabled = false;
setTimeout(() => { btn.textContent = 'Copy Diff'; }, 1500);
}
function copyDiff(btn) {
const pr = getPrInfo();
if (!pr) return;
const diffUrl = `${location.origin}/${pr.owner}/${pr.repo}/pull/${pr.number}.diff`;
btn.disabled = true;
btn.textContent = 'Copying...';
GM_xmlhttpRequest({
method: 'GET',
url: diffUrl,
onload: (res) => {
if (res.status >= 200 && res.status < 300) {
GM_setClipboard(res.responseText, 'text');
flash(btn, 'Copied!');
} else {
flash(btn, 'Failed');
}
},
onerror: () => flash(btn, 'Failed'),
});
}
function addCopyDiffButton() {
const pr = getPrInfo();
if (!pr) return;
const filesTab = document.querySelector('#prs-files-anchor-tab')
|| document.querySelector(`a[href$="/pull/${pr.number}/files"]`);
if (!filesTab) { dbg('skip: no filesTab'); return; }
if (document.getElementById('gh-copy-diff-btn')) { dbg('skip: btn already exists'); return; }
const btn = document.createElement('button');
btn.id = 'gh-copy-diff-btn';
btn.type = 'button';
btn.className = 'btn btn-sm';
btn.textContent = 'Copy Diff';
btn.style.marginLeft = '8px';
btn.addEventListener('click', (e) => {
e.preventDefault();
e.stopPropagation();
copyDiff(btn);
});
filesTab.insertAdjacentElement('afterend', btn);
dbg('INSERTED');
}
addCopyDiffButton();
const observer = new MutationObserver(() => {
addCopyDiffButton();
});
observer.observe(document.body, {
childList: true,
subtree: true
});
})();