When switched to the main branch, to prepare git pull pull remote master branch, are displayed prompts the local main branch 21 commits
problem causes:
Because you change the local master local master branch, you can select one of the following methods:
Keep the contents of the local master using git push origin, local modifications submitted directly to the remote
Modify or delete all local branches, remote synchronization to a local master, use git reset --hard origin / master
Reference links:
https://stackoverflow.com/questions/16288176/your-branch-is-ahead-of-origin-master-by-3-commits