chore(ci): add automatic merging of the release tag MONGOSH-2018 (#2379)

The new system requires us to manually merge into main. This automates that with a new workflow.

.github/workflows/merge-release-tag.yml

@@ -0,0 +1,33 @@
+name: Merge Release Tag
+
+on:
+  push:
+    tags:
+      - 'mongosh@[0-9]+.[0-9]+.[0-9]+'
+      - 'mongosh@[0-9]+.[0-9]+.[0-9]-rc.[0-9]+'
+  workflow_dispatch:
+
+permissions:
+  contents: none # We use the github app to checkout and push changes
+
+jobs:
+  merge-release-tag:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: mongodb-js/devtools-shared/actions/setup-bot-token@main
+        id: app-token
+        with:
+          app-id: ${{ vars.DEVTOOLS_BOT_APP_ID }}
+          private-key: ${{ secrets.DEVTOOLS_BOT_PRIVATE_KEY }}
+
+      - uses: actions/checkout@v4
+        with:
+          ref: main
+          fetch-depth: "0"
+          token: ${{ steps.app-token.outputs.token }}
+
+      - name: Merge release tag into main
+        run: |
+          git merge ${{ github.ref }} -m "chore(release): merge changes from ${{ github.ref_name }}"
+          git push origin main

packages/build/README.md

@@ -39,7 +39,7 @@ Execute the following steps to publish a new release:
    ```
    Follow the instructions and verify the inferred release version is correct.
 7. Wait for Evergreen to finish the publication stage.
-8. The previous step will have pushed tags for the npm publishes. Check out the tag for `mongosh@<version>` (not `v<version>`), create a branch for it, push that branch and open a PR with it. Then immediately merge that branch **using the `git merge` CLI command into main** and push to main. **NEVER** use the Github PR merge functionality, since that would squash the commit and give it a new commit hash that is different from the one in the tag.
+8. Ensure that the version bump was automatically merged into main and that it is synced up with the `mongosh@x.x.x` tag.
 9. Close the Jira ticket for the release, post an update in the `#mongosh` Slack channel and ping the docs team.
 
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