Git push rejected "non-fast-forward"

Question

It looks, that someone pushed new commits between your last git fetch and git push. In this case you need to repeat your steps and rebase my_feature_branch one more time.

git fetch
git rebase feature/my_feature_branch
git push origin feature/my_feature_branch

After the git fetch I recommend to examine situation with gitk --all.

Probably you did not fetch the remote changes before the rebase or someone pushed new changes (while you were rebasing and trying to push). Try these steps:

#fetching remote 'feature/my_feature_branch' branch to the 'tmp' local branch 
git fetch origin feature/my_feature_branch:tmp

#rebasing on local 'tmp' branch
git rebase tmp

#pushing local changes to the remote
git push origin HEAD:feature/my_feature_branch

#removing temporary created 'tmp' branch
git branch -D tmp

I had this problem! I tried: git fetch + git merge, but dont resolved! I tried: git pull, and also dont resolved

Then I tried this and resolved my problem (is similar of answer of Engineer):

git fetch origin master:tmp
git rebase tmp
git push origin HEAD:master
git branch -D tmp

I'm late to the party but I found some useful instructions in github help page and wanted to share them here.

Sometimes, Git can't make your change to a remote repository without losing commits. When this happens, your push is refused.

If another person has pushed to the same branch as you, Git won't be able to push your changes:

$ git push origin master
To https://github.com/USERNAME/REPOSITORY.git
 ! [rejected]        master -> master (non-fast-forward)
error: failed to push some refs to 'https://github.com/USERNAME/REPOSITORY.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.

You can fix this by fetching and merging the changes made on the remote branch with the changes that you have made locally:

$ git fetch origin
# Fetches updates made to an online repository
$ git merge origin YOUR_BRANCH_NAME
# Merges updates made online with your local work

Or, you can simply use git pull to perform both commands at once:

$ git pull origin YOUR_BRANCH_NAME
# Grabs online updates and merges them with your local work

I had a similar problem and I resolved it with: git pull origin

try this command

$ git push -f -u origin <name of branch>

i.e $ git push -f -u origin master