Configure special branches to auto-merge on push

The branches that will get merged on push are
* `release-next` into `main`
* `release-next` into `ornl-next`
* `ornl-next` into `main`

Author: peterfpeterson

.github/workflows/automerge.yml

@@ -0,0 +1,50 @@
+# this uses the action to merge special branches on push
+# https://github.com/marketplace/actions/merge-branch
+name: Merge protected branches
+on:
+  push:
+    branches:
+      - [ornl-next, release-next]
+
+jobs:
+  merge-relase-into-main:
+    runs-on: ubuntu-latest
+    if: ${{ github.ref == release-next }}
+    steps:
+      - uses: actions/checkout@master
+
+      - name: Merge release-next into main
+        uses: devmasx/merge-branch@master
+        with:
+          type: now
+          target_branch: main
+          message: Merge release-next into main
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+
+  merge-ornl-into-main:
+    runs-on: ubuntu-latest
+    if: ${{ github.ref == ornl-next }}
+    steps:
+      - uses: actions/checkout@master
+
+      - name: Merge ornl-next into main
+        uses: devmasx/merge-branch@master
+        with:
+          type: now
+          target_branch: main
+          message: Merge ornl-next into main
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+
+  merge-relase-into-ornl:
+    runs-on: ubuntu-latest
+    if: ${{ github.ref == release-next }}
+    steps:
+      - uses: actions/checkout@master
+
+      - name: Merge ornl-next into main
+        uses: devmasx/merge-branch@master
+        with:
+          type: now
+          target_branch: ornl-next
+          message: Merge release-next into ornl-next
+          github_token: ${{ secrets.GITHUB_TOKEN }}