`fatal: remote error: upload-pack: not our ref` trying to update submodules

When attempting to update the submodules in a local iTerm2 git repo, this error results:

fatal: remote error: upload-pack: not our ref 32204dadd9640719bdd8576f9fa1dea2605140da
fatal: Fetched in submodule path 'CoreParse', but it did not contain 32204dadd9640719bdd8576f9fa1dea2605140da. Direct fetching of that commit failed.

There are similar errors attempting to update the NMSSH and Sparkle submodules. I don't know, but it looks like you have local changes to these three submodules that you forgot to push to GitHub.