"git add -i" with path gives "Argument list too long"

Just ran "git add -i <path>" with "<path>" pointing to a subdirectory which happens to have a bunch of files in it (about 7k) and it barfed thusly:

   Can't exec "git": Argument list too long at /usr/local/libexec/git- 
core/git-add--interactive line 158.
   Died at /usr/local/libexec/git-core/git-add--interactive line 158.

I see that what it's trying to do under the hood is:

   git diff-index --cached --numstat --summary HEAD -- <7,000+ paths...>

Sure, we could divide the paths into smaller groups, run multiple invocations of "git diff-index", and concatenate the results. But it would be nicer if there was some other way that we could get at the same information without having to pass 7,000 paths explicitly on the command line; is there any which I am overlooking?

The enormous file list is the result of passing <path> into "git ls- files -- <path>". Would it be worth:

- either, modifying "git diff-index" to accept a list of paths over  
stdin so that we could at least pipe the output from "git ls-files"  
into "git diff-index"

- or, preferably, teach "git diff index" to recurse into directories  
rather than expect a list of paths-of-blobs (possibly with a command  
line switch to activate the behaviour if it were deemed a dangerous  
default)

This is one piece of plumbing that I've never dabbled with, so forgive me if my questions are a little dumb.

Cheers, Wincent