Extension to detect the type of merge based on the base branch

merge.js

const options = {
	master: 'merge',
	staging: 'squash'
};

const base = document.querySelector('#partial-discussion-header .base-ref').textContent.trim();

const what = options[base];

[...document.querySelectorAll('button[data-details-container=".js-merge-pr"]')].forEach(item => {
	item.disabled = true;
});

document.querySelector(`.select-menu-merge-method button[value="${what}"]`).click();

document.querySelector(`button[data-details-container=".js-merge-pr"][class*="${what}"]`).disabled = false;