Update README.md

Author: dabreadman

README.md

@@ -1,30 +1,51 @@
 # Sync Upstream Repo Fork
 
-This repository contains an github action to sync your current repository with an upstream repository. The work is greatly inspired by [actions-registry/github-repo-sync-upstream](https://github.com/actions-registry/github-repo-sync-upstream) which didn't work for me.
-Added parameter to determine target branch.
+This is a Github Action used to merge changes from remote.  
+
+This is forked from [mheene](https://github.com/mheene/sync-upstream-repo), with me adding authentication using [GitHub Token](https://docs.github.com/en/actions/reference/authentication-in-a-workflow) and downstream branch options due to the [default branch naming changes](https://github.com/github/renaming).
+
+## Use case
+
+- Perserve a repo while keeping up-to-date (rather than to clone it).
+- Have a branch in sync with upstream, and pull changes into dev branch.
 
 ## Usage
 
-Example github action:
+Example github action [here](https://github.com/THIS-IS-NOT-A-BACKUP/go-web-proxy/blob/main/.github/workflows/sync5.yml):
 
 ```YAML
-name: CI
+name: My_Pipeline_Name
 
-on: 
+### 
+env:
+  # Required, URL to upstream (fork base)
+  UPSTREAM_URL: "https://github.com/dabreadman/go-web-proxy.git"
+  # Optional, defaults to main
+  DOWNSTREAM_BRANCH: "main"
+### 
+
+on:
   schedule:
-    - cron: "15 14 * * *"
+    - cron: '30 * * * *'
 
 jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
-    - name: GitHub Sync to Upstream Repository
-      uses: dabreadman/[email protected]
-      with:
-      # GitHub public upstream repo
-        upstream_repo: https://github.com/holger24/AFD.git 
-        branch: main
+      - name: GitHub Sync to Upstream Repository
+        uses: dabreadman/[email protected]
+        with: 
+          upstream_repo: ${{ env.UPSTREAM_URL }}
+          branch: $$ env.DOWNSTREAM_BRANCH }}
+          token: ${{ secrets.GITHUB_TOKEN}}
 ```
 
-This action syncs your repo at branch `main` with the upstream repo ``` https://github.com/holger24/AFD.git ``` every day at 14:15 UTC.
+This action syncs your repo (merge changes from `remote`) at branch `main` with the upstream repo ``` https://github.com/dabreadman/go-web-proxy.git ``` every 30 minutes.
+
+## Mechanism
+
+1. Setup an environment using docker.
+  (Why do that when `Workflow` is inside an environment? I have no idea).
+2. Pass arguments into `entrypoint.sh`.
+3. `entrypoint.sh` does the heavy lifting.  
+  git clone, set origin/upstream, fetch, merge, push.