Adding file to git’s stage does nothing and cannot be committed

The final solution to this particular problem was to remove both web.config entries from the git cache, commit any changes, and re-add the desired Web.config file back to git.

git rm --cached path/to/Web.config
git rm --cached path/to/web.config
git commit -m "Repair confused cache"
git add path/to/Web.config
git commit -m "Add Web.config"