Tracking empty directories

[Jonathan Nieder <jrnieder@gmail.com>]

Jakub Narebski wrote:

> Also one needs to remember that this would require adding extension
> to git index, because currently it tracks only files, and not 
> directories.  Explicitly tracking directories in the index could be 
> useful for other purposes...
>
> The major difficulty of this is IMHO not the UI, but tracking all those
> tricky corner cases (like directory/file conflict, etc.).

I have ideas about how to resolve those tricky corner cases, but not
about what the UI should look like.  How does one go about adding a
directory?  Does it ever get implicitly removed?

Would this actually require an index extension, strictly speaking?
Certainly one ought to register an extension name or bump the version
number to avoid confusing gits that don't know about the feature.
But after that, couldn't we (e.g.) allow the directory name (ending
with '/') as index entry?

A related question is backward compatibility (both for alternative git
implementations and for scripts that did not know that "git ls-files"
might mention an empty directory) which somehow seems less
daunting. ;-)

Jonathan