[CI] Different approach to automating backports #501

Automates cherry-picking fixes to stable branches via [baackport X.Y] in commit messages or /backport X.Y comments, with conflict notification

Fixes #501

Author: atif09

.github/workflows/backport.yml

@@ -1,8 +1,9 @@
 name: Backport fixes to stable branch
 
 on:
-  pull_request_target:
-    types: [closed]
+  push:
+    branches:
+      - master
   issue_comment:
     types: [created]
 
@@ -11,18 +12,20 @@ permissions:
   pull-requests: write
 
 jobs:
-  backport:
+  backport-on-push:
+    if: github.event_name == 'push'
+    uses: ./.github/workflows/reusable-backport.yml
+    with:
+      commit_sha: ${{ github.sha }}
+
+  backport-on-comment:
     if: >
-      (
-        github.event_name == 'pull_request_target' &&
-        github.event.pull_request.merged
-      ) || (
-        github.event_name == 'issue_comment' &&
-        github.event.issue.pull_request &&
-        github.event.issue.state == 'closed' &&
-        contains(fromJSON('["MEMBER", "OWNER"]'), github.event.comment.author_association) &&
-        github.event.comment.body == '/backport'
-      )
+      github.event_name == 'issue_comment' &&
+      github.event.issue.pull_request &&
+      github.event.issue.state == 'closed' &&
+      contains(fromJSON('["MEMBER", "OWNER"]'), github.event.comment.author_association) &&
+      startsWith(github.event.comment.body, '/backport')
     uses: ./.github/workflows/reusable-backport.yml
     with:
-      source_pr_number: ${{ github.event.pull_request.number || github.event.issue.number }}
+      pr_number: ${{ github.event.issue.number }}
+      comment_body: ${{ github.event.comment.body }}

.github/workflows/reusable-backport.yml

@@ -88,18 +88,20 @@ jobs:
               --title "[backport] $PR_TITLE (to $BRANCH)" \
               --body "Backport of #$PR_NUMBER to \`$BRANCH\`."
           else
-            git cherry-pick --abort
-            gh pr comment "$PR_NUMBER" \
-              --body "❌ Cherry-pick to \`$BRANCH\` failed due to conflicts. Please backport manually:
-
-            \`\`\`bash
-            git fetch origin $BRANCH
-            git checkout -b backport/${PR_NUMBER}-to-${BRANCH} origin/$BRANCH
-            git cherry-pick -x $SHA
-            # resolve conflicts
-            git cherry-pick --continue
-            git push origin backport/${PR_NUMBER}-to-${BRANCH}
-            \`\`\`
-
-            Then open a PR targeting \`$BRANCH\`."
+            git cherry-pick --abort || true
+            {
+              echo "❌ Cherry-pick to \`$BRANCH\` failed due to conflicts. Please backport manually:"
+              echo ""
+              echo "\`\`\`bash"
+              echo "git fetch origin $BRANCH master"
+              echo "git checkout -b backport/${PR_NUMBER}-to-${BRANCH} origin/$BRANCH"
+              echo "git cherry-pick -x $SHA"
+              echo "# resolve conflicts"
+              echo "git cherry-pick --continue"
+              echo "git push origin backport/${PR_NUMBER}-to-${BRANCH}"
+              echo "\`\`\`"
+              echo ""
+              echo "Then open a PR targeting \`$BRANCH\`."
+            } > /tmp/backport-comment.md
+            gh pr comment "$PR_NUMBER" --body-file /tmp/backport-comment.md
           fi