How can I fix the 'sha' undefined error for my Netlify site? - jekyll

Question

So I've built a Jekyll site with the theme [Moon](Failed to persist entry: TypeError: Cannot read property 'sha' of undefined) and I've uploaded it to my GitHub repository. Then I want to add Netlify's admin panel to my site so I follow this guide which I modify the config.yml to the following code:
backend:
name: git-gateway
publish_mode: editorial_workflow
media_folder: "files"
display_url: https://ccsource.org
slug:
encoding: "ascii"
clean_accents: true
collections:
- name: "story"
label: "Story"
folder: "_posts"
extension: "md"
slug: "{{year}}-{{month}}-{{day}}-{{slug}}"
create: true
fields:
- {label: "Layout", name: "layout", widget: "hidden", default: "post"}
- {label: "Title", name: "title", widget: "string"}
- label: "tags"
name: "tags"
widget: "list"
allow_add: true
default: ["story"]
- {label: "Summary", name: "excerpt", widget: "string", required: false}
- {label: "comments", name: "comments", widget: "hidden", default: true}
- label: "Publish date"
name: "date"
widget: "datetime"
default: ""
format: "MMM Do YY"
- {label: "Body", name: "body", widget: "markdown", required: true}
Since I got markdown sample file like:
---
layout: post
title: "Sample"
date: 2016-03-15
excerpt: "Hello..."
tag:
- sample
- post
- video
comments: true
---
# Sample
But after all things setup and deployed I visit my site's admin panel and try to create a new post I keep getting the following error.
Failed to persist entry: TypeError: Cannot read property 'sha' of undefined
And I've googled and modified the branch value to site which match to my github repository, but the error keeps showing, how can I fix it?

Answer 1

For anyone else experiencing this, the issue was that Netlify Identity was enabled, but Git Gateway, a sub-feature of Netlify Identity, was not. Instructions for enabling Git Gateway here: https://www.netlify.com/docs/git-gateway/#getting-started