Make wtf bash < 4 compatible, fix -f handling.

contrib/wtf

@@ -11,9 +11,20 @@ _wtf()
     prev=${COMP_WORDS[COMP_CWORD-1]}
 
     [ "$prev" = -f ] && _filedir && return 0
+    [[ "$cur" == -* ]] && COMPREPLY=( -f ) && return 0
 
-    db=${ACRONYMDB:-/usr/share/misc/acronyms*}
-    COMPREPLY=( $( compgen -W "$( cut -f 1 -s $db )" -- "${cur^^}" ) )
+    set -- "${COMP_WORDS[@]}"
+    while [ $# -gt 0 ]; do
+        if [ "$1" = -f ]; then
+            shift ; db=$1 ; break
+        fi
+        shift
+    done
+    [ -z $db ] && db=${ACRONYMDB:-/usr/share/misc/acronyms*}
+
+    [ ${BASH_VERSINFO[0]} -ge 4 ] && cur="${cur^^}"
+
+    COMPREPLY=( $( compgen -W "$( cut -f 1 -s $db ) -f" -- "${cur}" ) )
 } &&
 complete -F _wtf $filenames wtf