/etc/bash_completion.d/axi-cache is in apt-xapian-index 0.45.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 | # axi-cache(1) completion
#
# © 2010, David Paleino <dapal@debian.org>
#
# This file is released under GPL-2, or later.
# This is for development only. It's normally defined inside bash-completion.
#have() { return 0; }
have axi-cache &&
_axi_cache() {
    local cur prev cmd
    COMPREPLY=()
    COMP_WORDBREAKS=${COMP_WORDBREAKS//:}
    type _get_comp_words_by_ref &>/dev/null && {
        _get_comp_words_by_ref -n: cur prev
    } || {
        cur=$(_get_cword ":")
        prev=${COMP_WORDS[$COMP_CWORD-1]}
    }
    cmd=${COMP_WORDS[1]}
    case "$prev" in
        *axi-cache*)
            COMPREPLY=( $(compgen -W "help more search show again showpkg showsrc depends rdepends policy madison" -- "$cur") )
            return 0
            ;;
        --sort)
            COMPREPLY=( $(compgen -W "$(egrep ^[a-z] /var/lib/apt-xapian-index/values | awk -F"\t" '{print $1}')" -- "$cur") )
            return 0
            ;;
    esac
    case "$cmd" in
        search|again)
            if [[ "$cur" == -* ]]; then
                COMPREPLY=( $(compgen -W "--sort --tags" -- "$cur") )
                return 0
            fi
            ;;
        show|showpkg|showsrc|depends|rdepends|policy|madison)
            if [[ "$cur" == -* ]]; then
                COMPREPLY=( $(compgen -W "--last" -- "$cur") )
                return 0
            fi
            ;;
        *)
            return 0
            ;;
    esac
    if [ -n "$cur" ]; then
        #unset COMP_WORDS[$COMP_CWORD]
        COMPREPLY=( $(compgen -W "$(${COMP_WORDS[@]} --tabcomplete=partial)" -- "$cur") )
    else
        COMPREPLY=( $(compgen -W "$(${COMP_WORDS[@]} --tabcomplete=plain)" -- "$cur") )
    fi
    return 0
} &&
complete -F _axi_cache axi-cache
 |