With trunk as of r936849:
$ ls ^
ls: ^: No such file or directory
$ svn add ^/
subversion/libsvn_client/cmdline.c:320: (apr_err=235000)
svn: In file 'subversion/libsvn_subr/dirent_uri.c' line 1641: assertion failed
(! svn_path_is_url(relative))
Abort trap (core dumped)
$
(gdb) bt
#0 0x0f7dd43d in kill () from /usr/lib/libc.so.53.1
#1 0x0f82a7af in abort () at /usr/src/lib/libc/stdlib/abort.c:68
#2 0x0f7373c9 in svn_error_abort_on_malfunction (can_return=1,
file=0x2f720da0 "subversion/libsvn_subr/dirent_uri.c", line=1641,
expr=0x2f7211c7 "! svn_path_is_url(relative)")
at subversion/libsvn_subr/error.c:601
#3 0x0f737419 in svn_error__malfunction (can_return=1,
file=0x2f720da0 "subversion/libsvn_subr/dirent_uri.c", line=1641,
expr=0x2f7211c7 "! svn_path_is_url(relative)")
at subversion/libsvn_subr/error.c:624
#4 0x0f734f03 in svn_dirent_get_absolute (pabsolute=0xcfbec258,
relative=0x80c8e988 "file:///tmp/svn-sandbox/repos", pool=0x88270018)
at subversion/libsvn_subr/dirent_uri.c:1641
#5 0x0e7fbaf6 in svn_client_add4 (
path=0x80c8e988 "file:///tmp/svn-sandbox/repos", depth=svn_depth_infinity,
force=0, no_ignore=0, add_parents=0, ctx=0x899487b8, pool=0x88270018)
at subversion/libsvn_client/add.c:592
#6 0x1c004ee4 in svn_cl__add (os=0x899481c0, baton=0xcfbec398,
pool=0x89948018) at subversion/svn/add-cmd.c:76
#7 0x1c010cad in main (argc=3, argv=0xcfbec59c) at subversion/svn/main.c:2304
(gdb)