<pre>
'fossil rm file' crashes:
(gdb) where
#0  0x91af1e9a in closedir$UNIX2003 ()
#1  0x00002d43 in del_directory_content (zDir=0x202b00 "mdb.mk") at add_.c:223
#2  0x00002de9 in del_cmd () at add_.c:255
#3  0x00022fb7 in main (argc=3, argv=0xbffff49c) at main_.c:258

mdb.mk is a plain file

Suggested patch:
--- src/add.c
+++ src/add.c
@@ -249,11 +249,11 @@
   db_begin_transaction();
   for(i=2; i<g.argc; i++){
     char *zName;

     zName = mprintf("%/", g.argv[i]);
-    if( file_isdir(zName) ){
+    if( file_isdir(zName) == 1){
       del_directory_content(zName);
     } else {
       char *zPath;
       Blob pathname;
       file_tree_name(zName, &pathname, 1);
</pre>