[SP-18628] Add Back-merge Workflow

.github/workflows/back-merge-handler.yml

@@ -0,0 +1,84 @@
+name: Back Merge handler
+
+on:
+  push:
+    branches:
+      - master
+      - stable
+
+jobs:
+  pr_master_to_stable:
+    runs-on: ubuntu-latest
+    if: github.ref_name == 'master'
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Check if PR exists
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          prs=$(gh pr list \
+              --repo "$GITHUB_REPOSITORY" \
+              --json baseRefName,headRefName \
+              --jq '
+                  map(select(.baseRefName == "stable" and .headRefName == "master"))
+                  | length
+              ')
+          if ((prs > 0)); then
+              echo "Pull Request already exists"
+              echo "SKIP=true" >> $GITHUB_ENV
+          fi
+
+      - name: Check if stable is ahead
+        run: |
+          commits=$(git rev-list origin/stable..origin/master --count)
+          if ((commits == 0)); then
+            echo "No diffs was found between branches"
+            echo "SKIP=true" >> $GITHUB_ENV
+          fi
+
+      - name: Create Pull Request
+        if: env.SKIP != 'true'
+        run: gh pr create -B stable -H master --title '[GitHub Actions] Merge master -> stable' --label back-merge --body 'Autogenerated Pull Request for `back-merge` triggered by Github Actions'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  pr_stable_to_develop:
+    runs-on: ubuntu-latest
+    if: github.ref_name == 'stable'
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Check if PR exists
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          prs=$(gh pr list \
+              --repo "$GITHUB_REPOSITORY" \
+              --json baseRefName,headRefName \
+              --jq '
+                  map(select(.baseRefName == "develop" and .headRefName == "stable"))
+                  | length
+              ')
+          if ((prs > 0)); then
+            echo "Pull Request already exists"
+            echo "SKIP=true" >> $GITHUB_ENV
+          fi
+
+      - name: Check if stable is ahead
+        run: |
+          commits=$(git rev-list origin/develop..origin/stable --count)
+          if ((commits == 0)); then
+            echo "No diffs was found between branches"
+            echo "SKIP=true" >> $GITHUB_ENV
+          fi
+
+      - name: Create Pull Request
+        if: env.SKIP != 'true'
+        run: gh pr create -B develop -H stable --title '[GitHub Actions] Merge stable -> develop' --label back-merge --body 'Autogenerated Pull Request for `back-merge` triggered by Github Actions'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}