completion

#!/usr/bin/env bash
    function _sync_py_remove_items {
        python3 - $@ <<EndOfPython
import sys
s = sys.argv[1]
for arg in s.split(' '):
    arg = arg.strip()
    if arg not in sys.argv[2:]:
        sys.stdout.write(arg + ' ')
sys.stdout.write('\n')
EndOfPython
    }

_sync_py() {

    local cur=${COMP_WORDS[COMP_CWORD]}
    local opts="-o --oneway -h --help"
    local syncfile_list="`cd && ls .sync_*`"
    local syncfile=
    local target=

    for ((i=1; i < $COMP_CWORD; i++)); do
        local word=${COMP_WORDS[i]}
        if [[ $opts =~ "$word" ]]; then
            # This is an option. Remove it from the list of remaining options.
            case "$word" in
            -o|--oneway)
                opts=`_sync_py_remove_items "$opts" -o --oneway`
                ;;
            -h|--help)
                opts=`_sync_py_remove_items "$opts" -h --help`
                ;;
            esac
        else
            # We've found a non-option argument. If we haven't seen a syncfile
            # yet, it's that. Otherwise, it's a target directory.
            if [[ -z "$syncfile" ]]; then
                syncfile="$word"
            elif [[ -n "$syncfile" && -z "$target" ]]; then
                target="$word"
            fi
        fi
    done

    COMPREPLY=( $(compgen -W " $opts" -- "$cur") )
    if [[ -z "$syncfile" ]]; then
        COMPREPLY+=( $(compgen -W "$syncfile_list" -- "$cur") )
    elif [[ -n "$syncfile" && -z "$target" ]]; then
        COMPREPLY+=( $(compgen -d -- "$cur") )
    fi
}
complete -o filenames -F _sync_py sync.py