allow custom diff header labels

lib/util/diff.js

@@ -13,16 +13,25 @@ const toBase64 = str => Buffer.from(str, 'utf-8').toString('base64');
  * terrible terrible terrible string diff helper for debugging
  * @param {string} a
  * @param {string} b
+ * @param {object} page Page object from the API, used to generate diff labels
  */
-export function diff (a, b) {
+export function diff (a, b, page) {
+	let labels = null;
+	if (page) { // generate diff labels based on
+		labels = [
+			`${page.title}  (${page.revid ? `revision ${page.revid}` : 'current revision'}${page.timestamp ? ` from ${page.timestamp}` : ''})`,
+			`${page.title}  (pending edit)`,
+		];
+	}
 	// base64 input strings before passing to shell to avoid escaping issues
 	// https://stackoverflow.com/a/60221847
-	// use tail to cut off useless file info lines
+	// use tail to cut off file info lines and re-add with fake filenames/dates
-	execSync(String.raw`bash <<- EOF
+	// this function is so extra now holy shit
+	execSync(String.raw`bash <<- 'EOF'
 		diff --color=always -u \
-			<(echo "${toBase64(a)}" | base64 -d) \
+			${labels ? `--label="$(echo '${toBase64(labels[0])}' | base64 -d)" ` : ''}<(echo '${toBase64(a)}' | base64 -d) \
-			<(echo "${toBase64(b)}" | base64 -d) \
+			${labels ? `--label="$(echo '${toBase64(labels[1])}' | base64 -d)" ` : ''}<(echo '${toBase64(b)}' | base64 -d) \
-		| tail -n +3
+		${labels ? `|| true` : `| tail -n +3` /* cut off header if no labels */}
 	EOF`, {
 		// display result directly in terminal
 		stdio: 'inherit',