SourceTreeで「error: failed to push some refs to」の対処法

git -c diff.mnemonicprefix=false -c core.quotepath=false --no-optional-locks push -v --tags origin master:master
Pushing to http://xxxxx/testuser/examples.git
 ! [rejected]        master -> master (non-fast-forward)
error: failed to push some refs to 'http:/xxxxx/testuser/examples.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.



エラー終了しました。エラーの内容は上記をご覧ください。