Adding script and workflow to automate the preparation of releases (open-telemetry#615)

The prepare-release workflow is triggered when a new release/<version> branch
is created. This workflow parses the <version> number from the branch name and
updates version.py/changelog.md files accordingly. It then creates a pull
request with those changes.

This addresses part of open-telemetry#374.

Co-authored-by: Mauricio Vásquez <[email protected]>

Author: 2 people

Diff for: .github/workflows/prepare-release.yml

@@ -0,0 +1,27 @@
+name: prepare-release
+on:
+  push:
+    branch: [ 'release/*' ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Get the version
+      id: get_version
+      run: echo ::set-output name=VERSION::${GITHUB_REF/refs\/tags\//}
+
+    - name: Prepare the release
+      id: update
+      run: |
+        ./scripts/prepare_release.sh ${{ steps.get_version.outputs.VERSION }}
+
+    - name: Create Pull Request
+      id: create-pr
+      uses: peter-evans/[email protected]
+      with:
+        branch: ${{ steps.get_version.outputs.VERSION }}-auto
+        title: '[pre-release] Update changelogs, version [${{ steps.get_version.outputs.VERSION }}]'
+      if: ${{ steps.update.outputs.version_updated == 1 }}

Diff for: scripts/prepare_release.sh

@@ -0,0 +1,80 @@
+#!/bin/bash
+#
+# This script:
+#   1. parses the version number from the branch name
+#   2. updates version.py files to match that version
+#   3. iterates through CHANGELOG.md files and updates any files containing
+#      unreleased changes
+#   4. sets the output variable 'version_updated' to determine whether
+#      the github action to create a pull request should run. this allows
+#      maintainers to merge changes back into the release branch without
+#      triggering unnecessary pull requests
+#
+
+VERSION=`echo $1 | awk -F "/" '{print $NF}'`
+echo "Using version ${VERSION}"
+
+# check the version matches expected versioning e.g
+# 0.6, 0.6b, 0.6b0, 0.6.0
+if [[ ! "${VERSION}" =~ ^([0-9])(\.*[0-9]{1,5}[a-b]*){1,3}$ ]]; then
+    echo "Version number invalid: $VERSION"
+    exit 1
+fi
+
+function update_version_file() {
+    errors=0
+    for f in `find . -name version.py`; do
+        # check if version is already in version.py
+        grep -q ${VERSION} $f;
+        rc=$?
+        if [ $rc == 0 ]; then
+            errors=1
+            echo "${f} already contains ${VERSION}"
+            continue
+        fi
+        # update version.py
+        perl -i -pe "s/__version__.*/__version__ = \"${VERSION}\"/g" ${f};
+        git add ${f};
+        echo "Updating ${f}"
+    done
+    if [ ${errors} != 0 ]; then
+        echo "::set-output name=version_updated::0"
+        exit 0
+    fi
+}
+
+function update_changelog() {
+    errors=0
+    for f in `find . -name CHANGELOG.md`; do
+        # check if version is already in CHANGELOG
+        grep -q ${VERSION} $f;
+        rc=$?
+        if [ $rc == 0 ]; then
+            errors=1
+            echo "${f} already contains ${VERSION}"
+            continue
+        fi
+        # check if changelog contains any new details
+        changes=`sed -n '/## Unreleased/,/^##/p' ${f} | grep -v '^##'  | wc -w | awk '{$1=$1;print}'`
+        if [ ${changes} != "0" ]; then
+            # update CHANGELOG.md
+            perl -i -pe 's/## Unreleased.*/## Unreleased\n\n## '${VERSION}'/' ${f};
+            git add ${f};
+            echo "Updating ${f}"
+        else
+            echo "Skipping ${f}, no changes detected"
+        fi
+    done
+    if [ ${errors} != 0 ]; then
+        echo "::set-output name=version_updated::0"
+        exit 0
+    fi
+}
+
+update_version_file
+update_changelog
+
+git config --local user.email "[email protected]"
+git config --local user.name "GitHub Action"
+git commit -m "updating changelogs and version to ${VERSION}"
+echo "::set-output name=version_updated::1"