mod-times (was: keyword expansion)

[tony.luck@intel.com]

> I am aware that keyword expansion is at the moment at the very bottom of
> the todo list. However I need it. Has someone something ready to use? I
> am looking for the following informations:
> 
> 	- Time stamp of the last modification of a file

One way to do this would be to rip on some of the core fundamentals of GIT
and store the time that an object was created inside the object. E.g.

   blob size secs-since-1970 ...

Then "read-tree" could fill this into the cache, and checkout-cache could
set the mod-time on the file when it creates it, which would mean that you
could see the timestamp for a file simply by using "ls -l file".

I think we'd need some other justifications before this would stand any
hope of getting in though, since it makes such a huge incompatible change
to the basic GIT format :-)  Maybe queue the idea for GIT2.0?

-Tony