git commit -am "revert changes on this file, not finished with it yet"
push it, no force needed:
git push
get back to your unfinished work, again do (3 times arrow up):
git checkout HEAD^ -- /path/to/file
effectively 'uncommitting':
To modify the last commit of the repository HEAD, obfuscating your accidentally pushed work, while potentially running into a conflict with your colleague who may have pulled it already, and who will grow grey hair and lose lots of time trying to reconcile his local branch head with the central one:
To remove file change from last commit:
to revert the file to the state before the last commit, do:
git checkout HEAD^ /path/to/file
to update the last commit with the reverted file, do:
git commit --amend
to push the updated commit to the repo, do:
git push -f
Really, consider using the preferred method mentioned before.