automatically removing missing files beneath a directory

If I have a subdirectory in a git repository, and I remove some files without telling git, is there is a simple way to automatically run the equivalent of 'git rm' for all the missing files? git commit -a would work, except that I only want to remove files beneath a particular subdirectory. git add <directory> does the equivalent operation for adding files, but I don't see a way to automatically remove them without parsing the output of git status.

Thanks, Geoffrey