/usr/share/bash-completion/completions/fdformat is in util-linux 2.25.2-6.
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  | _fdformat_module()
{
	local cur prev OPTS
	COMPREPLY=()
	cur="${COMP_WORDS[COMP_CWORD]}"
	prev="${COMP_WORDS[COMP_CWORD-1]}"
	case $prev in
		'-h'|'--help'|'-V'|'--version')
			return 0
			;;
	esac
	DEVS=$(for I in echo /dev/fd*; do if [ -e $I ]; then echo $I; fi; done)
	OPTS="--no-verify --help --version $DEVS"
	COMPREPLY=( $(compgen -W "${OPTS[*]}" -- $cur) )
	return 0
}
complete -F _fdformat_module fdformat
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