remark-modified-time.mjs

import { execSync } from "child_process";

export function remarkModifiedTime() {
    return function (tree, file) {
        const filepath = file.history[0];
        const result = execSync(`git log -1 --pretty="format:%cI" "${filepath}"`);
        file.data.astro.frontmatter.lastModified = result.toString();
    };
}