tools: generate authors list automatically

* Add new `update-authors.js` tool that traverses commit history using
  `git log` and creates authors list.

* Decouple common functions into a module shared between tools.

* Add `.mailmap` file with proper names and emails of active
  collaborators.  This file is automatically parsed by Git so that
  `git log --format='%aN <%aE>'` won't show duplicate entries in case
  something was committed with misconfigured Git.  E.g., without this
  file @tshemsedinov appears twice in the list, as Timur Shemsedinov
  and as tshemsedinov, but with mailmap applied Git automatically
  coalesces these entries to use the full name only.

.mailmap

@@ -0,0 +1,3 @@
+Timur Shemsedinov <timur.shemsedinov@gmail.com>
+Alexey Orlenko <eaglexrlnk@gmail.com>
+Mykola Bilochub <nbelochub@gmail.com>

tools/common.js

@@ -0,0 +1,27 @@
+// Common utilities used by tools
+'use strict';
+
+const childProcess = require('child_process');
+const fs = require('fs');
+
+const common = {};
+module.exports = common;
+
+common.getCommandOutput = (cmd) => {
+  const exec = common.promisify(childProcess.exec);
+  return exec(cmd).then((stdout, stderr) => {
+    if (stderr) console.error(stderr);
+    return stdout;
+  });
+};
+
+common.promisify = (fn) => (...args) => (
+  new Promise((resolve, reject) => {
+    fn(...args, (error, ...result) => {
+      if (error) reject(error);
+      else resolve(...result);
+    });
+  })
+);
+
+common.writeFile = common.promisify(fs.writeFile);

tools/prepare-release.js

@@ -2,11 +2,11 @@
 
 'use strict';
 
-const childProcess = require('child_process');
-const fs = require('fs');
 const https = require('https');
 const path = require('path');
 
+const { getCommandOutput, writeFile } = require('./common');
+
 const commandName = path.relative('.', __filename);
 const help = `\
 This tool allows to filter the result of
@@ -83,14 +83,6 @@ getCommandOutput('git cherry ' + branch).then((cherryOut) => {
   process.exit(1);
 });
 
-function getCommandOutput(cmd) {
-  const exec = promisify(childProcess.exec);
-  return exec(cmd).then((stdout, stderr) => {
-    if (stderr) console.error(stderr);
-    return stdout;
-  });
-}
-
 function getMetadata(commitHash) {
   const command = 'git log --format="%aN%n%B" -n 1 ' + commitHash;
   return getCommandOutput(command).then((output) => {
@@ -188,17 +180,6 @@ function getStreamData(stream, callback) {
   stream.on('error', callback);
 }
 
-function promisify(fn) {
-  return (...args) => (
-    new Promise((resolve, reject) => {
-      fn(...args, (error, ...result) => {
-        if (error) reject(error);
-        else resolve(...result);
-      });
-    })
-  );
-}
-
 function processCommits(commits) {
   commits = filterCommits(commits, maxLevel);
 
@@ -233,7 +214,6 @@ function processCommits(commits) {
 
   script += '\n';
 
-  const writeFile = promisify(fs.writeFile);
   return Promise.all([
     writeFile(`${branch}-apply-commits.sh`, script),
     writeFile(`${branch}-commits.md`, changelog)

tools/update-authors.js

@@ -0,0 +1,24 @@
+#!/usr/bin/env node
+
+'use strict';
+
+const path = require('path');
+const { getCommandOutput, writeFile } = require('./common');
+
+const AUTHORS_PATH = path.resolve(__dirname, '..', 'AUTHORS');
+
+getCommandOutput('git log --reverse --format="%aN <%aE>"').then((out) => {
+  const seen = new Set();
+  const authors = out.split('\n').reduce((list, author) => {
+    if (!seen.has(author)) {
+      list.push(author);
+      seen.add(author);
+    }
+    return list;
+  }, []);
+  return writeFile(AUTHORS_PATH, authors.join('\n'));
+}).catch((error) => {
+  const message = error.stack || error.toString();
+  console.error(message);
+  process.exit(1);
+});