How do I push amended commit to the remote Git repository?

I actually once pushed with --force and .git repository and got scolded by Linus BIG TIME. In general this will create a lot of problems for other people. A simple answer is "Don't do it".

I see others gave the recipe for doing so anyway, so I won't repeat them here. But here is a tip to recover from the situation after you have pushed out the amended commit with --force (or +master).

1. Use git reflog to find the old commit that you amended (call it old, and we'll call the new commit you created by amending new).
2. Create a merge between old and new, recording the tree of new, like git checkout new && git merge -s ours old.
3. Merge that to your master with git merge master
4. Update your master with the result with git push . HEAD:master
5. Push the result out.

Then people who were unfortunate enough to have based their work on the commit you obliterated by amending and forcing a push will see the resulting merge will see that you favor new over old. Their later merges will not see the conflicts between old and new that resulted from your amending, so they do not have to suffer.

You are seeing a Git safety feature. Git refuses to update the remote branch with your branch, because your branch's head commit is not a direct descendent of the current head commit of the branch that you are pushing to.

If this were not the case, then two people pushing to the same repository at about the same time would not know that there was a new commit coming in at the same time and whoever pushed last would lose the work of the previous pusher without either of them realising this.

If you know that you are the only person pushing and you want to push an amended commit or push a commit that winds back the branch, you can 'force' Git to update the remote branch by using the -f switch.

git push -f origin master

Even this may not work as Git allows remote repositories to refuse non-fastforward pushes at the far end by using the configuration variable receive.denynonfastforwards. If this is the case the rejection reason will look like this (note the 'remote rejected' part):

 ! [remote rejected] master -> master (non-fast forward)

To get around this, you either need to change the remote repository's configuration or as a dirty hack you can delete and recreate the branch thus:

git push origin :master
git push origin master

In general the last parameter to git push uses the format <local_ref>:<remote_ref>, where local_ref is the name of the branch on the local repository and remote_ref is the name of the branch on the remote repository. This command pair uses two shorthands. :master has a null local_ref which means push a null branch to the remote side master, i.e. delete the remote branch. A branch name with no : means push the local branch with the given name to the remote branch with the same name. master in this situation is short for master:master.