git selective revert local changes from a file

I believe you can do it most simply with:

git checkout -p <optional filename(s)>

From the manpage:

   −p, −−patch
       Interactively select hunks in the difference between the <tree−ish>
       (or the index, if unspecified) and the working tree. The chosen
       hunks are then applied in reverse to the working tree (and if a
       <tree−ish> was specified, the index).

       This means that you can use git checkout −p to selectively discard
       edits from your current working tree.

You can do that directly with git checkout -p. See Daniel Stutzbach's answer below.

Old answer (before checkout -p was introduced):

You can do it like this:

git add -i

(select the hunks you want to keep)

git commit -m "tmp"

Now you have a commit with only the changes you want to keep, and the rest is unstaged.

git reset --hard HEAD

At this point, uncommitted changes have been discarded, so you have a clean working directory, with the changes you want to keep committed on top.

git reset --mixed HEAD^

This removes the last commit ('tmp'), but keeps the modifications in your working directory, unstaged.

EDIT: replaced --soft with --mixed, to clean up the staging area.