git push Error Updates were rejected because the tip of your current branch is behind

DannideMacBook-Pro:connect-cas2-client danni$ git push origin master
To https://gitee.com/danni3/connect-cas2-client.git
 ! [rejected]        master -> master (non-fast-forward)
error: failed to push some refs to 'https://gitee.com/danni3/connect-cas2-client.git'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Integrate the remote changes (e.g.
hint: 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

Solution: git pull origin master

DannideMacBook-Pro:connect-cas2-client danni$ git pull origin master
From https://gitee.com/danni3/connect-cas2-client
 * branch            master     -> FETCH_HEAD
fatal: refusing to merge unrelated histories

git pull origin master—allow-unrelated-histories