compare-screenshots: output PR comment template

After taking screenshots, output an HTML table template that can be
copied into a PR comment. The absolute paths serve as placeholders
that can be selected and replaced by uploading the images.

The paths are placed on their own lines so that users can easily
triple-click to select the entire path, copy it, and then paste
the uploaded image URL in its place.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

script/compare-screenshots.js

@@ -240,6 +240,25 @@ async function main() {
     console.error(`\nScreenshots saved:`);
     console.error('  - .before.png');
     console.error('  - .after.png');
+
+    console.error(`\nPR comment template (copy paths, then replace by uploading images):\n`);
+    console.log(`<!-- Generated by 'node ${
+      process.argv
+        .slice(1)
+        .map((e, i) => i != 1 ? e : e.replace(/.*[/\\]/, ''))
+        .join(' ')
+    }' -->`);
+    console.log(`<table>`);
+    console.log(`<tr><th>Before</th><th>After</th></tr>`);
+    console.log(`<tr>`);
+    console.log(`<td>`);
+    console.log(path.resolve('.before.png'));
+    console.log(`</td>`);
+    console.log(`<td>`);
+    console.log(path.resolve('.after.png'));
+    console.log(`</td>`);
+    console.log(`</tr>`);
+    console.log(`</table>`);
   } finally {
     await browser.close();
   }