It seems I did something wrong:
$ git add .
$ git status
On branch master
nothing to commit, working directory clean
$ git commit -m 'Task #2 after accepting'
On branch master
nothing to commit, working directory clean
$ git push origin master
To https://my_repository@bitbucket.org/my_repository/bla.git
! [rejected] master -> master (fetch first)
error: failed to push some refs to 'https://my_repository@bitbucket.org/my_repository/bla.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
I don't know what to do to make GIT work as before and I don't remember, that I did something with git local directory except moving local repository in other folder.