Github failed to sync this branch

Describes the cause and action for error messages.

Error Message(English)：
failed to sync this branch

Resolution

GitHub - Failed to sync this branch
https://stackoverflow.com/questions/35375516/github-failed-to-sync-this-branch

Github Merge Fail due to unmerged files
https://stackoverflow.com/questions/30953338/github-merge-fail-due-to-unmerged-files

GitHub Failed to sync this branch
https://stackoverflow.com/questions/22721688/github-failed-to-sync-this-branch

Reset local git repository
https://stackoverflow.com/questions/11910921/reset-local-git-repository

GitHub Error: "Failed To Sync This Branch. You Might Need To Open A ...
https://www.youtube.com/watch?v=w2M5CAonYqY

https://www.youtube.com/watch?v=w2M5CAonYqY

GitHub for Windowsでsyncが失敗する - kiliwave
http://kiliwave.hatenablog.com/entry/2015/03/18/122800

GitHub Desktop for Windowsの"failed to sync this branch"の対処 - test.py
http://testpy.hatenablog.com/entry/2017/09/24/003000

Git Hub が Faild を出してきたらローカル・ディスクにファイルが多すぎる ...
https://qiita.com/muzudho1/items/90e2ce5a6e24991dcd72