Gatsby: [v2] whole page re-renders on navigation

[sokki]

Description

I'm not sure if this is already a known problem but I could not find a related issue.

Steps to reproduce

gatsby new my-default-project https://github.com/gatsbyjs/gatsby-starter-default#v2
cd my-default-project && npm run develop
open Browser and look into dev-tools

Expected result

When navigating to a different page, only parts of the DOM should update.

Actual result

Every DOM node gets recreated. Including the root element.

Environment

  System:
    OS: macOS High Sierra 10.13.6
    CPU: x64 Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
    Shell: 5.3 - /bin/zsh
  Binaries:
    Node: 8.9.4 - ~/.nvm/versions/node/v8.9.4/bin/node
    Yarn: 1.6.0 - /usr/local/bin/yarn
    npm: 6.1.0 - ~/.nvm/versions/node/v8.9.4/bin/npm
  Browsers:
    Chrome: 67.0.3396.99
    Safari: 11.1.2
  npmPackages:
    gatsby: next => 2.0.0-beta.40 
    gatsby-plugin-react-helmet: next => 3.0.0-beta.3 
  npmGlobalPackages:
    gatsby-cli: 2.0.0-beta.6

[LekoArts]

Here you go:
https://github.com/gatsbyjs/gatsby/issues/6127