First complete version

Dummy config :)

package.json

@@ -0,0 +1,15 @@
+{
+  "name": "puller",
+  "version": "1.0.0",
+  "description": "puller",
+  "main": "puller.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "MIT",
+  "dependencies": {
+    "@octokit/rest": "^16.13.3",
+    "xmlhttprequest": "^1.8.0"
+  }
+}

puller.js

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+global.XMLHttpRequest = require("xmlhttprequest").XMLHttpRequest;
+
+const Octokit = require('@octokit/rest');
+
+exports.puller = async () => {
+    const openMergeRequest = () => {
+        const octokit = new Octokit({
+            auth: `token ${process.env.GITHUB_TOKEN}`
+        });
+        return octokit.pulls.create({
+            owner: process.env.baseRepoOwner,
+            repo: process.env.repoName,
+            head: `${process.env.headRepoOwner}:${process.env.headRepoBranch}`,
+            base: process.env.baseRepoBranch,
+            title: 'Automatic syncing pull request',
+            body: `Automatic syncing pull request for ${new Date()}`,
+            maintainer_can_modify: false
+        });
+    };
+
+    const handleError = error => {
+        if (error.name === "HttpError" &&
+            error.status === 422 &&
+            error.errors) {
+            let message = error.errors[0].message;
+            if (message.includes('No commits between'))
+                return {
+                    status: 'Success',
+                    message: 'No commits found'
+                };
+            else if (message.includes('A pull request already exists'))
+                return {
+                    status: 'Success',
+                    message: 'A pull request already exists'
+                };
+            else
+                return error;
+        } else
+            return error;
+    };
+
+    return openMergeRequest()
+        .then(() => {
+            const message = {
+                status: 'Success',
+                message: 'Pull request created'
+            };
+            console.log(message);
+            return message;
+        })
+        .catch(error => {
+            const message = handleError(error);
+            console.log(message);
+            return message;
+        });
+};