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"

Typically when git gets into a confused state, removing and re-adding the file to the cache will fix it:

git rm --cached foo

It seems the most common way that a file gets in the confused state, is when performing a mv from the command line.
I've found that using git mv instead of mv helps to prevent running into this issue. http://linux.die.net/man/1/git-mv

Lastly, If you are going to delete a file from a git repository, use git rm instead of just rm
Why use 'git rm' to remove a file instead of 'rm'?

https://www.kernel.org/pub/software/scm/git/docs/git-rm.html`