gitのpushがrejectされた

pushしたらなんかエラーが出てpushできない

$ git push origin [remote branch]
! [rejected]        [branch] -> [remote branch] (non-fast-forward)
error: failed to push some refs to 'git@reposicoty.git'
To prevent you from losing history, non-fast-forward updates were rejected
Merge the remote changes (e.g. 'git pull') before pushing again.  See the
'Note about fast-forwards' section of 'git push --help' for details.

色々調べたけど解決しないし時間ないからbranchもういっこ切ってそっちにmergeしてからpushしたんだけど、うっかりそのままbranch切ったら

$ git branch [branch2]
warning: refname '[branch]' is ambiguous.
fatal: Ambiguous object name: '[branch]'.

じゃなくて

$ git checkout master
$ git branch [branch2]
$ git merge [branch]
$ git push origin [remote branch]

これで解決した