Split up customJS into customHTML and customJS for better organisation (#5981)

* WIP

* fixed customJS not actually working in footer

* Moving scripts to footer, #5980

* Added upgrade scripts for #5980

src/upgrades/1.7.0/generate-custom-html.js

@@ -0,0 +1,37 @@
+'use strict';
+
+var meta = require('../../meta');
+
+module.exports = {
+	name: 'Generate customHTML block from old customJS setting',
+	timestamp: Date.UTC(2017, 9, 12),
+	method: function (callback) {
+		var newHTML = meta.config.customJS;
+		var newJS = [];
+
+		// Forgive me for parsing HTML with regex...
+		var scriptMatch = /^<script\s?(?!async|deferred)?>([\s\S]+?)<\/script>/m;
+		var match = scriptMatch.exec(newHTML);
+
+		while (match) {
+			if (match[1]) {
+				// Append to newJS array
+				newJS.push(match[1].trim());
+
+				// Remove the match from the existing value
+				newHTML = ((match.index > 0 ? newHTML.slice(0, match.index) : '') + newHTML.slice(match.index + match[0].length)).trim();
+			}
+
+			match = scriptMatch.exec(newHTML);
+		}
+
+		// Combine newJS array
+		newJS = newJS.join('\n\n');
+
+		// Write both values to config
+		meta.configs.setMultiple({
+			customHTML: newHTML,
+			customJS: newJS,
+		}, callback);
+	},
+};