Simplified porcelains?

"git checkout HEAD" doesn't do anything (expect possibly display a bit of useful information).
It's "git checkout HEAD ." (note the filename "." at the end) that will discard uncommitted
changes, because (like in CVS), it's a request to cause the working directory to match "HEAD"
with respect to the path ".".

But I think that section shouldn't really be in that document; it's talking about a
non-recommended method for keeping two computers in sync by confusing one of them and then
intentionally losing the false changes that the computer thinks it has.

Git is actually extremely careful about uncommitted changes. The only ways to lose uncommitted
changes with git are to either ask to discard them (with "checkout <filename>" or "reset") or
ask to have working-directory files modified or removed (e.g., "apply" or "rm"). By default,
git won't even overwrite modified working directory files with merge results like other
version control systems will.