Simplifies backmerge to master->develop PR

Author: AndrewSazonov

.github/workflows/backmerge-pr.yaml

@@ -1,8 +1,7 @@
 # This workflow creates a backmerge PR into `develop` whenever a new version tag is pushed (v*).
 #
 # Key points:
-# - The PR head is a temporary branch that points at the *tag commit* (refs/tags/vX.Y.Z).
-#   After merging, `develop` can `git describe` as vX.Y.Z-... because the tag commit becomes an ancestor.
+# - Creates a PR from `master` to `develop` when a new tag is pushed.
 # - The PR is auto-merged using a MERGE COMMIT (not squash) via a GitHub App token.
 #   The GitHub App must be added to the develop ruleset bypass list.
 #
@@ -12,10 +11,11 @@
 # - Actions secret:   ES_BACKMERGE_PRIVATE_KEY  (GitHub App private key PEM)
 # - Actions variable: ES_BACKMERGE_APP_ID       (GitHub App ID)
 
-name: Backmerge PR (tag -> develop)
+name: Backmerge PR (master -> develop)
 
 on:
   push:
+    branches: ['patch']
     tags: ['v*']
 
 permissions:
@@ -34,64 +34,49 @@ jobs:
           app-id: ${{ vars.BACKMERGE_APP_ID }}
           private-key: ${{ secrets.BACKMERGE_PRIVATE_KEY }}
 
-      - name: Checkout tag commit
+      - name: Checkout repository
         uses: actions/checkout@v5
         with:
-          ref: ${{ github.ref }} # refs/tags/vX.Y.Z
           fetch-depth: 0
           token: ${{ steps.app-token.outputs.token }}
 
-      - name: Create and push backmerge branch at tag
-        id: vars
+      - name: Create PR from master to develop (or reuse if exists)
+        id: pr
         run: |
           set -euo pipefail
 
           TAG='${{ github.ref_name }}'
-          BRANCH="backmerge/${TAG}"
 
-          echo "tag=${TAG}" >> "$GITHUB_OUTPUT"
-          echo "branch=${BRANCH}" >> "$GITHUB_OUTPUT"
+          TITLE="Backmerge: ${TAG} from master into develop"
 
-          git config user.name  "github-actions[bot]"
-          git config user.email "github-actions[bot]@users.noreply.github.com"
+          BODY="⚠️ This PR is created automatically for backmerge of the release tag \`${TAG}\` from \`master\` into \`develop\`.
 
-          # Create/move branch to point exactly at the tag commit
-          git checkout -B "$BRANCH"
+          It is labeled \`[maintainer] auto-pull-request\` and is excluded from release notes and version bump logic."
 
-          # Push (force makes re-runs idempotent for the same tag)
-          git push --force --set-upstream origin "$BRANCH"
-        env:
-          GITHUB_TOKEN: ${{ steps.app-token.outputs.token }}
-
-      - name:
-          Create PR from tag backmerge branch to develop (or reuse if exists)
-        run: |
-          set -euo pipefail
-
-          TITLE="Backmerge: ${{ steps.vars.outputs.tag }} into develop"
-
-          BODY="⚠️ This PR is created automatically for backmerge of a new release tag commit \`${{ steps.vars.outputs.tag }}\` into \`develop\`.
-
-          It is labeled `[maintainer] auto-pull-request` and is excluded from release notes and version bump logic."
+          # Check if a PR from master to develop already exists
+          EXISTING_PR=$(gh pr list --repo "${{ github.repository }}" --base develop --head master --state open --json number --jq '.[0].number // empty')
 
-          if gh pr view --repo "${{ github.repository }}" --head "${{ steps.vars.outputs.branch }}" >/dev/null 2>&1; then
-            echo "PR already exists for head=${{ steps.vars.outputs.branch }}"
+          if [ -n "$EXISTING_PR" ]; then
+            echo "PR #${EXISTING_PR} already exists for master -> develop"
+            echo "pr_number=${EXISTING_PR}" >> "$GITHUB_OUTPUT"
           else
-            gh pr create \
+            PR_URL=$(gh pr create \
               --repo "${{ github.repository }}" \
               --base develop \
-              --head "${{ steps.vars.outputs.branch }}" \
+              --head master \
               --title "$TITLE" \
               --label "[maintainer] auto-pull-request" \
-              --body "$BODY"
+              --body "$BODY")
+            PR_NUMBER=$(echo "$PR_URL" | grep -oE '[0-9]+$')
+            echo "Created PR #${PR_NUMBER}"
+            echo "pr_number=${PR_NUMBER}" >> "$GITHUB_OUTPUT"
           fi
         env:
           GH_TOKEN: ${{ steps.app-token.outputs.token }}
 
       - name: Enable auto-merge using MERGE COMMIT
         run: |
           set -euo pipefail
-          # Merge the PR identified by its head branch.
-          gh pr merge --repo "${{ github.repository }}" --merge --auto "${{ steps.vars.outputs.branch }}"
+          gh pr merge --repo "${{ github.repository }}" --merge --auto "${{ steps.pr.outputs.pr_number }}"
         env:
           GH_TOKEN: ${{ steps.app-token.outputs.token }}