commit 939f796f086cac17ad0558b36fa87c55a9cb1a22
Author: Nicholas Marriott <nicholas.marriott@gmail.com>
Date:   Thu Aug 1 23:40:44 2013 +0100

    Don't leak formats if they are added multiple times.

--- a/format.c
+++ b/format.c
@@ -117,6 +117,7 @@
 format_add(struct format_tree *ft, const char *key, const char *fmt, ...)
 {
 	struct format_entry	*fe;
+	struct format_entry	*fe_now;
 	va_list			 ap;
 
 	fe = xmalloc(sizeof *fe);
@@ -126,7 +127,13 @@
 	xvasprintf(&fe->value, fmt, ap);
 	va_end(ap);
 
-	RB_INSERT(format_tree, ft, fe);
+	fe_now = RB_INSERT(format_tree, ft, fe);
+	if (fe_now != NULL) {
+		free(fe_now->value);
+		fe_now->value = fe->value;
+		free(fe->key);
+		free(fe);
+	}
 }
 
 /* Find a format entry. */