zsh: better fix for partial completions

Properly handle relative paths followed by partial filenames
hg add ../path/to/file/partial[TAB]

contrib/zsh_completion

@@ -178,6 +178,7 b' typeset -A _hg_cmd_globals'
 }
 
 _hg_status() {
+  [[ -d $PREFIX ]] || PREFIX=$PREFIX:h
   status_files=(${(ps:\0:)"$(_hg_cmd status -0n$1 ./$PREFIX 2>/dev/null)"})
 }