Ghost/core/server/web/parent/middleware/ghost-locals.js

const ghostVersion = require('../../../lib/ghost-version');
const themeService = require('../../../../frontend/services/themes');

// ### GhostLocals Middleware
// Expose the standard locals that every request will need to have available
module.exports = function ghostLocals(req, res, next) {
    // Make sure we have a locals value.
    res.locals = res.locals || {};
    // The current Ghost version
    res.locals.version = ghostVersion.full;
    // The current Ghost version, but only major.minor
    res.locals.safeVersion = ghostVersion.safe;
    // relative path from the URL
    res.locals.relativeUrl = req.path;
    // make ghost api version available for the theme + routing
    res.locals.apiVersion = themeService.getApiVersion();

    next();
};