Teach roll_versions.py how to update CHANGELOG.md files.

sky/tools/roll_versions.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import os
+import subprocess
 import yaml
 import xml.etree.ElementTree as ET
 
+
 PUBSPECS = [
     'sky/sdk/pubspec.yaml',
     'mojo/public/dart/pubspec.yaml',
     'mojo/dart/mojo_services/pubspec.yaml',
     'mojo/dart/mojom/pubspec.yaml',
 ]
 
 MANIFESTS = [
     'sky/apk/demo/AndroidManifest.xml',
 ]
@@ skipping 12 matching lines @@
     return '.'.join(pieces)
 
 
 def sort_dict(unsorted):
     sorted_dict = collections.OrderedDict()
     for key in sorted(unsorted.keys()):
         sorted_dict[key] = unsorted[key]
     return sorted_dict
 
 
+def count_commits(start, end):
+    return subprocess.check_output([
+        'git', 'rev-list', '%s...%s' % (start, end)]).count('\n')
+
+
+def last_commit_to(file_path):
+    return subprocess.check_output(['git', 'log', '-1', '--format=%h', file_path]).strip()
+
+
 def update_pubspec(pubspec):
     # TODO(eseidel): This does not prserve any manual sort-order of the yaml.
     with open(pubspec, 'r') as stream:
         spec = yaml.load(stream)
         old_version = spec['version']
         spec['version'] = increment_version(old_version)
         print "%20s  %6s => %6s" % (spec['name'], old_version, spec['version'])
 
     with open(pubspec, 'w') as stream:
         yaml.dump(spec, stream=stream, default_flow_style=False)
+    return spec['version']
+
+
+def update_changelog(changelog, pubspec, version):
+    old = last_commit_to(pubspec)
+    new = last_commit_to('.')
+    url = "https://github.com/domokit/mojo/compare/%s...%s" % (old, new)
+    count = count_commits(old, new)
+    message = """## %s
+
+  - %s changes: %s
+
+""" % (version, count, url)
+    prepend_to_file(message, changelog)
 
 
 def prepend_to_file(to_prepend, filepath):
     with open(filepath, 'r+') as f:
         content = f.read()
         f.seek(0, 0)
         f.write(to_prepend + content)
 
 
 def update_manifest(manifest):
     VERSION_CODE = '{http://schemas.android.com/apk/res/android}versionCode'
     VERSION_NAME = '{http://schemas.android.com/apk/res/android}versionName'
     tree = ET.parse(manifest)
     root = tree.getroot()
     package_name = root.get('package')
     old_code = root.get(VERSION_CODE)
     old_name = root.get(VERSION_NAME)
     root.set(VERSION_CODE, increment_version(old_code))
     root.set(VERSION_NAME, increment_version(old_name))
     print "%20s  %6s (%s) => %6s (%s)" % (package_name, old_name, old_code,
         root.get(VERSION_NAME), root.get(VERSION_CODE))
     # TODO(eseidel): This isn't smart enough to wrap/intent multi-attribute
     # elements like <manifest> as is the typical AndroidManifiest.xml style
     # we could write our own custom prettyprinter to do that?
     tree.write(manifest)
     prepend_to_file(MANIFEST_PREFACE, manifest)
 
 
 def main():
+    # Should chdir to the root directory.
+
     print 'Pub packages:'
     for pubspec in PUBSPECS:
-        update_pubspec(pubspec)
+        new_version = update_pubspec(pubspec)
+        changelog = os.path.join(os.path.dirname(pubspec), 'CHANGELOG.md')
+        update_changelog(changelog, pubspec, new_version)
 
     # TODO(eseidel): Without this ET uses 'ns0' for 'android' which is wrong.
     ET.register_namespace('android', 'http://schemas.android.com/apk/res/android')
 
     print 'APKs:'
     for manifest in MANIFESTS:
         update_manifest(manifest)
 
 
 if __name__ == '__main__':
     main()