diff --git a/README.md b/README.md
index 6e56bc0..8cdabfa 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,7 @@
 The GitHub Actions for pushing to GitHub repository local changes authorizing using GitHub token.
 
 With ease:
+
 - update new code placed in the repository, e.g. by running a linter on it,
 - track changes in script results using Git as archive,
 - publish page using GitHub-Pages,
@@ -43,7 +44,7 @@ jobs:
 | name | value | default | description |
 | ---- | ----- | ------- | ----------- |
 | github_token | string | | Token for the repo. Can be passed in using `${{ secrets.GITHUB_TOKEN }}`. |
-| branch | string | main | Destination branch to push changes. Can be passed in using `${{ github.ref }}`. |
+| branch | string | (default) | Destination branch to push changes. Can be passed in using `${{ github.ref }}`. |
 | force | boolean | false | Determines if force push is used. |
 | tags | boolean | false | Determines if `--tags` is used. |
 | directory | string | '.' | Directory to change to before pushing. |
diff --git a/start.js b/start.js
index 0e10b40..db5953f 100644
--- a/start.js
+++ b/start.js
@@ -1,22 +1,62 @@
+'use strict';
 const spawn = require('child_process').spawn;
 const path = require("path");
+const https = require('https');
 
-const exec = (cmd, args=[]) => new Promise((resolve, reject) => {
-    console.log(`Started: ${cmd} ${args.join(" ")}`)
-    const app = spawn(cmd, args, { stdio: 'inherit' });
-    app.on('close', code => {
-        if(code !== 0){
-            err = new Error(`Invalid status code: ${code}`);
-            err.code = code;
-            return reject(err);
-        };
-        return resolve(code);
-    });
-    app.on('error', reject);
-});
+const get = (url, options = {}) => new Promise((resolve, reject) => https
+    .get(url, options, (res) => {
+        const chunks = [];
+        res.on('data', (chunk) => chunks.push(chunk));
+        res.on('end', () => {
+            const body = Buffer.concat(chunks).toString('utf-8');
+            if (res.statusCode < 200 || res.statusCode > 300) {
+                return reject(Object.assign(
+                    new Error(`Invalid status code: ${res.statusCode}`),
+                    { res, body }
+                ));
+            }
+            return resolve(body)
+        });
+    })
+    .on('error', reject)
+)
+
+const exec = (cmd, args = [], options = {}) => new Promise((resolve, reject) =>
+    spawn(cmd, args, { stdio: 'inherit', ...options })
+        .on('close', code => {
+            if (code !== 0) {
+                return reject(Object.assign(
+                    new Error(`Invalid exit code: ${code}`),
+                    { code }
+                ));
+            };
+            return resolve(code);
+        })
+        .on('error', reject)
+);
+
+const trimLeft = (value, charlist = '/') => value.replace(new RegExp(`^[${charlist}]*`), '');
+const trimRight = (value, charlist = '/') => value.replace(new RegExp(`[${charlist}]*$`), '');
+const trim = (value, charlist) => trimLeft(trimRight(value, charlist));
 
 const main = async () => {
-    await exec('bash', [path.join(__dirname, './start.sh')]);
+    let branch = process.env.INPUT_BRANCH;
+    const repository = trim(process.env.INPUT_REPOSITORY);
+    if (!branch) {
+        const headers = {
+            'User-Agent': 'github.com/ad-m/github-push-action'
+        };
+        if (process.env.GITHUB_TOKEN) headers.Authorization = `token ${process.env.GITHUB_TOKEN}`;
+        const body = JSON.parse(await get(`https://api.github.com/repos/${repository}`, { headers }))
+        branch = body.default_branch;
+    }
+    await exec('bash', [path.join(__dirname, './start.sh')], {
+        env: {
+            ...process.env,
+            INPUT_BRANCH: branch,
+            INPUT_REPOSITORY: repository,
+        }
+    });
 };
 
 main().catch(err => {