build(zone.js): update gulp task to gen changelog automatically (#31915)

PR Close #31915

packages/zone.js/CHANGELOG.md

@@ -1,5 +1,5 @@
 <a name="0.10.1"></a>
-# [0.10.1](https://github.com/angular/angular/compare/zone.js-0.10.0...zone.js-0.10.1) (2019-07-30)
+## [0.10.1](https://github.com/angular/angular/compare/zone.js-0.10.0...zone.js-0.10.1) (2019-08-02)
 
 
 ### Bug Fixes

packages/zone.js/DEVELOPER.md

@@ -80,17 +80,19 @@ yarn webdriver-sauce-test
 Releasing
 ---------
 
-- create a new tag in `angular` repo.
+For example, the current version is `0.9.1`, and we want to release a new version `0.10.0`.
+
+- create a new tag in `angular` repo. The `tag` must be `zone.js-<version>`, so in this example we need to create the tag `zone.js-0.10.0`.
 
 ```
-$ TAG=<TAG>
+$ TAG=zone.js-0.10.0
 $ git tag $TAG
 ```
 
-- create a PR to update `changelog` of zone.js
+- Create PR to update `changelog` of zone.js, we need to define the previous tag which will be the current version.
 
 ```
-$ export PREVIOUS_ZONE_TAG=<PREVIOUS ZONE RELEASE TAG>
+$ export PREVIOUS_ZONE_TAG=zone.js-0.9.1
 $ yarn gulp changelog:zonejs
 ```
 

tools/gulp-tasks/changelog-zonejs.js

@@ -10,8 +10,15 @@ module.exports = (gulp) => () => {
   const tag = process.env.TAG;
   const ptag = process.env.PREVIOUS_ZONE_TAG;
   const conventionalChangelog = require('gulp-conventional-changelog');
+  // the tag of zone.js will start with `zone.js-`, such as `zone.js-0.10.0`
+  // we will remove the first 8 (zone.js-) chars to get the real version.
+  const version = tag.replace(/^zone\.js-/, '');
   return gulp.src('packages/zone.js/CHANGELOG.md')
-      .pipe(conventionalChangelog({preset: 'angular'}, {}, {
+      .pipe(conventionalChangelog(
+          {
+            preset: 'angular',
+          },
+          {linkCompare: true, previousTag: ptag, currentTag: tag, version: version}, {
             // Ignore commits that have a different scope than `zone.js`.
             extendedRegexp: true,
             grep: '^[^(]+\\(zone\\.js\\)',