travis: Generate changelog for tags

.travis.yml

@@ -10,10 +10,11 @@ env:
     - IMAGE_NAME="$(basename -s '.git' ${TARGET_REPO})_${IMAGE_VERSION}.img"
 git:
   depth: 50
-matrix:
+jobs:
   fast_finish: true
   include:
-    - name: "Raspberry Pi Image Build"
+    - stage: Build
+      name: "Raspberry Pi Image Build"
       cache:
         directories:
         - imgcache
@@ -40,7 +41,8 @@ matrix:
           tags: true
         draft: true
         name: ${TRAVIS_TAG}
-    - name: "Documentation"
+    - stage: Build
+      name: "Documentation"
       language: node_js
       node_js:
         - "10"
@@ -66,7 +68,17 @@ matrix:
 #        target-branch: gh-pages
 #        on:
 #          branch: WIP/gitbook-autobuild
-
+    - stage: Annotate
+      name: Auto-generate changelog
+      language: python
+      python: 3.6
+      install:
+        - pip install GitPython PyGithub
+      script:
+        - PYTHONUNBUFFERED=1 python ./gen_changelog.py
+stages:
+  - Build
+  - Annotate
 # More info there
 # https://github.com/travis-ci/travis-ci/issues/6893
 # https://docs.travis-ci.com/user/customizing-the-build/

gen_changelog.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+
+# Generate and upload changelog
+
+from git import Repo, exc
+from github import Github
+import os
+import sys
+
+upload_changelog = True
+
+try:
+    current_tag = os.environ['TRAVIS_TAG']
+    if current_tag == '':
+        current_tag = 'HEAD'
+        upload_changelog = False
+    print('TRAVIS_TAG is set to {}'.format(current_tag))
+except KeyError:
+    print('TRAVIS_TAG not set - not uploading changelog')
+    current_tag = 'HEAD'
+    upload_changelog = False
+
+try:
+    api_key = os.environ['GITHUB_OAUTH_TOKEN']
+except KeyError:
+    print('GITHUB_OAUTH_TOKEN not set - not uploading changelog')
+    api_key = None
+    upload_changelog = False
+
+try:
+    repo_slug = os.environ['TRAVIS_REPO_SLUG']
+except KeyError:
+    print('TRAVIS_REPO_SLUG not set - cannot determine remote repository')
+    repo_slug = ''
+    exit(1)
+
+if len(sys.argv) > 1:
+    repo_path = sys.argv[1]
+else:
+    repo_path = '.'
+
+print('Opening repository at {}'.format(repo_path))
+repo = Repo(repo_path)
+git = repo.git()
+try:
+    print('Unshallowing repository')
+    git.fetch('--unshallow', '--tags')
+except exc.GitCommandError:
+    print('Repository already unshallowed')
+print('Attempting to get previous tag')
+base_tag = git.describe('--tags', '--abbrev=0', '{}^'.format(current_tag))
+print('Base tag set to {}'.format(base_tag))
+
+changelog = git.log('{}...{}'.format(base_tag, current_tag), '--pretty=format:* %H %s *(%an)*')
+print('Current changelog: \n{}'.format(changelog))
+
+# Only interact with Github if uploading is enabled
+if upload_changelog:
+    gh = Github(api_key)
+    gh_repo = gh.get_repo(repo_slug)
+    # Get all releases and find ours by its tag name
+    gh_release = None
+    for release in gh_repo.get_releases():
+        if release.tag_name == current_tag:
+            gh_release = release
+    if gh_release is None:
+        # We could not find the correct release, so here's our last resort. It will most likely fail.
+        gh_release = gh_repo.get_release(current_tag)
+    gh_body = gh_release.body
+    if gh_body is None:
+        gh_body = ''
+    gh_body = '{}\nChanges between `{}` and `{}`:\n\n{}'.format(gh_body, base_tag, current_tag, changelog)
+    print('New release body: {}'.format(gh_body))
+    gh_release.update_release(gh_release.tag_name, gh_body, draft=True, prerelease=True,
+                              tag_name=gh_release.tag_name, target_commitish=gh_release.target_commitish)