_filedir: avoid duplicate dirs internally, and a compgen -d call for …

…files

Not having duplicates in completions here is useful so we can sometimes
check if a _filedir resulted in only one completion. The previous
implementation resulted in duplicate dirs internally.

bash_completion

@@ -559,25 +559,34 @@ _filedir()
     local -a toks
     local reset
 
-    reset=$(shopt -po noglob); set -o noglob
-    toks=( $(compgen -d -- "$cur") )
-    IFS=' '; $reset; IFS=$'\n'
-
-    if [[ "$1" != -d ]]; then
+    if [[ "$1" == -d ]]; then
+        reset=$(shopt -po noglob); set -o noglob
+        toks=( $(compgen -d -- "$cur") )
+        IFS=' '; $reset; IFS=$'\n'
+    else
         local quoted
         _quote_readline_by_ref "$cur" quoted
 
         # Munge xspec to contain uppercase version too
         # http://thread.gmane.org/gmane.comp.shells.bash.bugs/15294/focus=15306
-        local xspec=${1:+"!*.@($1|${1^^})"}
+        local xspec=${1:+"!*.@($1|${1^^})"} plusdirs=()
+
+        # Use plusdirs to get dir completions if we have a xspec; if we don't,
+        # there's no need, dirs come along with other completions. Don't use
+        # plusdirs quite yet if fallback is in use though, in order to not ruin
+        # the fallback condition with the "plus" dirs.
+        local opts=( -f -X "$xspec" )
+        [[ $xspec ]] && plusdirs=(-o plusdirs)
+        [[ ${COMP_FILEDIR_FALLBACK-} ]] || opts+=( "${plusdirs[@]}" )
+
         reset=$(shopt -po noglob); set -o noglob
-        toks+=( $(compgen -f -X "$xspec" -- $quoted) )
+        toks+=( $(compgen "${opts[@]}" -- $quoted) )
         IFS=' '; $reset; IFS=$'\n'
 
         # Try without filter if it failed to produce anything and configured to
         [[ -n ${COMP_FILEDIR_FALLBACK:-} && -n "$1" && ${#toks[@]} -lt 1 ]] && {
             reset=$(shopt -po noglob); set -o noglob
-            toks+=( $(compgen -f -- $quoted) )
+            toks+=( $(compgen -f "${plusdirs[@]}" -- $quoted) )
             IFS=' '; $reset; IFS=$'\n'
         }
     fi