List Git commits not pushed to the origin yet

how to determine if a commit with particular hash have been pushed to the origin already?

# list remote branches that contain $commit
git branch -r --contains $commit

git log origin/master..master

or, more generally:

git log <since>..<until>

You can use this with grep to check for a specific, known commit:

git log <since>..<until> | grep <commit-hash>

Or you can also use git-rev-list to search for a specific commit:

git rev-list origin/master | grep <commit-hash>