zsh: fix completions with relative paths

hg add ../foo/bar[TAB] now does what you expect

contrib/zsh_completion

@@ -178,7 +178,7 b' typeset -A _hg_cmd_globals'
 }
 
 _hg_status() {
-  status_files=(${(ps:\0:)"$(_hg_cmd status -0n$1 . 2>/dev/null)"})
+  status_files=(${(ps:\0:)"$(_hg_cmd status -0n$1 ./$PREFIX 2>/dev/null)"})
 }
 
 _hg_unknown() {