docs: add RELEASING.md onboarding guide

Author: shuoweil

packages/bigframes/RELEASING.md

@@ -0,0 +1,63 @@
+# Releasing BigQuery DataFrames (BigFrames) on GitHub
+
+This onboarding documentation describes how to release a new version of the `bigframes` package.
+
+---
+
+## Why is this a manual step?
+By default in this monorepo, BigQuery DataFrames releases are marked with `skip_release: true`. This prevents automatic release pipelines from triggering on every commit. Instead, a library maintainer must explicitly trigger the release staging process using the `legacylibrarian` tool.
+
+---
+
+## Quick Onboarding Checklist (First Time Only)
+
+1.  **Install the legacylibrarian CLI tool**:
+    ```bash
+    go install github.com/googleapis/librarian/cmd/legacylibrarian@latest
+    ```
+    *(Ensure `~/go/bin` is in your system `PATH`)*.
+
+2.  **Authenticate with GitHub CLI**:
+    Ensure the `gh` tool is installed and logged in:
+    ```bash
+    gh auth login
+    ```
+
+---
+
+## How to Trigger a Release
+
+Follow these general steps to release a new version (e.g., `X.X.X`):
+
+1.  **Set your GitHub Auth Token**:
+    ```bash
+    export LIBRARIAN_GITHUB_TOKEN=$(gh auth token)
+    ```
+
+2.  **Checkout the main branch**:
+    ```bash
+    git fetch origin main && git checkout origin/main
+    ```
+
+3.  **Run the staging command with push**:
+    ```bash
+    legacylibrarian release stage \
+      --repo=https://github.com/googleapis/google-cloud-python \
+      --library=bigframes \
+      --library-version=X.X.X \
+      --push
+    ```
+    *   This automatically clones the repo in a temp folder, updates version references, creates a commit, pushes the release branch, and generates a Pull Request on GitHub.
+    *   Review the generated PR on GitHub, verify the `release:pending` label, and squash-merge it once tests pass.
+
+---
+
+## Detailed Step-by-Step & Troubleshooting
+
+For the detailed step-by-step cheatsheet, including troubleshooting common errors like:
+*   Context-Aware Access (CAA) credential blocks
+*   Git `insteadOf` redirection errors in `~/.gitconfig`
+*   `go-git` cleanliness errors caused by local `.vscode/` or `venv` directories
+
+Refer to the cheat-sheet document:
+👉 **[packages/bigframes/release-procedure.md](file:///usr/local/google/home/shuowei/src/google-cloud-python/google-cloud-python/packages/bigframes/release-procedure.md)**