+2  A: 

Looks you need to put that commit back into the master branch (if it belongs there). Also it looks like you’ve detached HEAD because that commit is not a branch head. If all this is true, try the following:

# git log -1

Remember the commit ID.

# git checkout master
# git reset --hard <commit-id>

Now gitk will show the yellow commit right next to the master marker and git push will be working again.

As to how you got into that situation, the only thing I can imagine is that you used git reset to reset the master branch to a previous commit but have not changed the currently checked-out commit.

Bombe
Perfect. Thanks!
rick