Re: [PATCH] checkout: add 'pre-checkout' hook

> >  worktree.  The hook is given three parameters: the ref of the previous HEAD,
> >  the ref of the new HEAD (which may or may not have changed), and a flag
> >  indicating whether the checkout was a branch checkout (changing branches,
> >  flag=1) or a file checkout (retrieving a file from the index, flag=0).
> > -This hook cannot affect the outcome of 'git-checkout'.
> > +This hook can prevent the checkout from proceeding by exiting with an
> > +error code.
> >  
> >  It is also run after 'git-clone', unless the --no-checkout (-n) option is
> >  used. The first parameter given to the hook is the null-ref, the second the
> >  ref of the new HEAD and the flag is always 1.
> >  
> > +This hook can be used to perform any clean-up deemed necessary before
> > +checking out the new branch/files.
> > +
> > +post-checkout
> > +-----------
> 
> This is not about your patch, but the patch text shows that our diff
> algorithm seems to have a room for improvement.  I expected to see a
> straight insersion of block of text, not touching anything in the original
> section on post-checkout hook.