Re: [PATCH 2/2] Add keyword unexpansion support to convert.c

> 
> On Tue, 17 Apr 2007, Andy Parkins wrote:
>> Adding expansion is harder, as I have no clue which calls to make to find
>> even the most basic information about an object; but I thought I'd get
>> feedback before I expend that effort.
> 
> Adding expansion is not just "harder". It's basically impossible to do 
> with any kind of performance.
> 
> Think "git checkout newbranch".
> 
> And think what we do about files (and whole subdirectories!) that haven't 
> even changed. And finally, think about how important that optimization is 
> in an SCM like git that supports branches.