1 files changed, 10 insertions, 0 deletions
diff --git a/builtin.h b/builtin.h
index 46cc789789..cb0db67681 100644
--- a/builtin.h
+++ b/builtin.h
@@ -107,6 +107,16 @@ void setup_auto_pager(const char *cmd, int def);
 
 int is_builtin(const char *s);
 
+/*
+ * Builtins which do not use RUN_SETUP should never see
+ * a prefix that is not empty; use this to protect downstream
+ * code which is not prepared to call prefix_filename(), etc.
+ */
+#define BUG_ON_NON_EMPTY_PREFIX(prefix) do { \
+	if ((prefix)) \
+		BUG("unexpected prefix in builtin: %s", (prefix)); \
+} while (0)
+
 int cmd_add(int argc, const char **argv, const char *prefix);
 int cmd_am(int argc, const char **argv, const char *prefix);
 int cmd_annotate(int argc, const char **argv, const char *prefix);