tools: add mailmap support for Co-authored-by tags

Support `.mailmap` for manually added `Author:` and
`Co-authored-by:` tags.

PR-URL: #26383
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Benjamin Gruenbaum <[email protected]>

Author: addaleax

Diff for: tools/update-authors.js

@@ -3,6 +3,7 @@
 // Passing --dry will redirect output to stdout rather than write to 'AUTHORS'.
 'use strict';
 const { spawn } = require('child_process');
+const path = require('path');
 const fs = require('fs');
 const readline = require('readline');
 
@@ -22,6 +23,38 @@ else
 
 output.write('# Authors ordered by first contribution.\n\n');
 
+const mailmap = new Map();
+{
+  const lines = fs.readFileSync(path.resolve(__dirname, '../', '.mailmap'),
+                                { encoding: 'utf8' }).split('\n');
+  for (let line of lines) {
+    line = line.trim();
+    if (line.startsWith('#') || line === '') continue;
+
+    let match;
+    // Replaced Name <[email protected]>
+    if (match = line.match(/^([^<]+)\s+(<[^>]+>)$/)) {
+      mailmap.set(match[2], { author: match[1] });
+    // <[email protected]> <[email protected]>
+    } else if (match = line.match(/^<([^>]+)>\s+(<[^>]+>)$/)) {
+      mailmap.set(match[2], { email: match[1] });
+    // Replaced Name <[email protected]> <[email protected]>
+    } else if (match = line.match(/^([^<]+)\s+(<[^>]+>)\s+(<[^>]+>)$/)) {
+      mailmap.set(match[3], {
+        author: match[1], email: match[2]
+      });
+    // Replaced Name <[email protected]> Original Name <[email protected]>
+    } else if (match =
+        line.match(/^([^<]+)\s+(<[^>]+>)\s+([^<]+)\s+(<[^>]+>)$/)) {
+      mailmap.set(match[3] + '\0' + match[4], {
+        author: match[1], email: match[2]
+      });
+    } else {
+      console.warn('Unknown .mailmap format:', line);
+    }
+  }
+}
+
 const seen = new Set();
 
 // Support regular git author metadata, as well as `Author:` and
@@ -34,7 +67,13 @@ rl.on('line', (line) => {
   const match = line.match(authorRe);
   if (!match) return;
 
-  const { author, email } = match.groups;
+  let { author, email } = match.groups;
+
+  const replacement = mailmap.get(author + '\0' + email) || mailmap.get(email);
+  if (replacement) {
+    ({ author, email } = { author, email, ...replacement });
+  }
+
   if (seen.has(email) ||
       /@chromium\.org/.test(email) ||
       email === '<[email protected]>') {