On Fri, Apr 03, 2009 at 05:02:16PM +0200, Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:
> 1) as it is all too easy, but not 2) as that would require too much work, 
> which would be overkill.

What about something trivial like this?

diff --git a/builtin-add.c b/builtin-add.c
index cb67d2c..a3d798e 100644
--- a/builtin-add.c
+++ b/builtin-add.c
@@ -164,6 +164,10 @@ int interactive_add(int argc, const char **argv, const char *prefix)
 	const char **args;
 	const char **pathspec = NULL;
 
+#ifdef NO_PERL
+	return error("git was compiled without perl support.");
+#endif
+
 	if (argc) {
 		pathspec = validate_pathspec(argc, argv, prefix);
 		if (!pathspec)

This way it would be more explicit that it was disabled and the
situation is not about -i was removed in some new versions or anything.