In order to push up through a given commit run the following command:
$ git push <remotename> <commit SHA>:<remotebranchname>
provided <remotebranchname> already exists on the remote. If it doesn't, you can use git push <remotename> <commit SHA>:refs/heads/<remotebranchname> to autocreate it.
In case you want to push a commit without pushing previous commits, you should first use git rebase -i to re-order the commits.