How do I reset the working tree without moving HEAD?

Question

Given a git branch with some commits on it (C is the most recent commit):

A -> B -> C

How do I reset my workspace so that all the files are in the state they were at commit B, but HEAD is still at C?

I've looked at git-reset, but none of the options seem to help. The man page suggests that all the different modes will move HEAD:

--soft
   Does not touch the index file or the working tree at all 
   (but resets the head to <commit>, just like all modes do).

I've tried git reset HEAD~ but that moves HEAD.

Answer 1

git checkout [-p|--patch] [<tree-ish>] [--] <pathspec>...

git checkout with <paths> or --patch is used to restore modified or deleted paths to their original contents from the index or replace paths with the contents from a named <tree-ish> (most often a commit-ish).

So you need to run this at root of your repository (works fine for any sub-tree or file(s) too):

git checkout HEAD~ -- .

This will result in git applying changes necessary to revert files to HEAD~ state, the changes will be in the index.