Unity Cloud Build bitbucket error push Changes

Hello .
When I am trying To upload changes to bitbucket this error message appear on source tree

git -c diff.mnemonicprefix=false -c core.quotepath=false --no-optional-locks push -v --tags --set-upstream origin master:master
Pushing to https://.git
To https://
.git
! [rejected] master → master (non-fast-forward)
error: failed to push some refs to https://_______________________________.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.

,Hello.
When Iam trying to upload changes to bit bucket it failed and send me this error

git -c diff.mnemonicprefix=false -c core.quotepath=false --no-optional-locks push -v --tags --set-upstream origin master:master
Pushing to https://.git
To https://
.git
! [rejected] master → master (non-fast-forward)
error: failed to push some refs to ‘https://_______________________________.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.

how is that related to unity cloud build?

it explicitly says: you have to pull before you can push

because when ever i make some changes this error happens unity did not allow us to use file version control with unity always refs got wrong and no body touches remote repository only me and i cant make push again .
this is always happen