/usr/share/yash/completion/chown is in yash 2.35-2.
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 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 | # (C) 2010 magicant
# Completion script for the "chown" command.
# Supports POSIX 2008, GNU coreutils 8.4, FreeBSD 8.1, OpenBSD 4.8, NetBSD 5.0,
# Mac OS X 10.6.3, SunOS 5.10, HP-UX 11i v3.
function completion/chown {
	case $("${WORDS[1]}" --version 2>/dev/null) in
		(*'coreutils'*) typeset type=GNU ;;
		(*)             typeset type="$(uname 2>/dev/null)" ;;
	esac
	case $type in
		(GNU) typeset long=true ;;
		(*)   typeset long= ;;
	esac
	typeset OPTIONS POSIXOPTIONS ADDOPTIONS ARGOPT PREFIX
	POSIXOPTIONS=( #>#
	"h ${long:+--no-dereference}; change the owner of symbolic links"
	"H; follow symbolic links to directories in operands (with -R)"
	"L; follow all symbolic links to directories (with -R)"
	"P; don't follow any symbolic links (with -R)"
	"R ${long:+--recursive}; recursively change the owner of files in a directory"
	) #<#
	ADDOPTIONS=()
	case $type in (GNU|*BSD|Darwin|SunOS)
		ADDOPTIONS=("$ADDOPTIONS" #>#
		"f ${long:+--silent --quiet}; suppress error messages"
		) #<#
		case $type in (GNU|NetBSD|FreeBSD|Darwin)
			ADDOPTIONS=("$ADDOPTIONS" #>#
			"v ${long:+--verbose}; print a message for each file processed"
			) #<#
		esac
	esac
	case $type in
	(GNU)
		ADDOPTIONS=("$ADDOPTIONS" #>#
		"c --changes; print a message when a change has been made"
		"--dereference; change the owner of files referred to by symbolic links"
		"--from:; specify an owner:group only from which changes are made"
		"--no-preserve-root; cancel the --preserve-root option"
		"--preserve-root; don't recursively change the owner of the root directory"
		"--reference:; specify a file to whose owner changes are made"
		"--help"
		"--version"
		) #<#
		;;
	(FreeBSD)
		ADDOPTIONS=("$ADDOPTIONS" #>#
		"x; stop recursion when reaching a different file system"
		) #<#
		;;
	esac
	OPTIONS=("$POSIXOPTIONS" "$ADDOPTIONS")
	unset POSIXOPTIONS ADDOPTIONS
	typeset ownergroup=false
	command -f completion//parseoptions ${long:+-es}
	case $ARGOPT in
	(-)
		command -f completion//completeoptions
		;;
	(--reference)
		complete -P "$PREFIX" -f
		;;
	(--from)
		ownergroup=true
		;;
	(*)
		command -f completion//getoperands
		if [ ${WORDS[#]} -eq 0 ]; then
			ownergroup=true
		else
			complete -f
		fi
		;;
	esac
	if $ownergroup; then
		case ${TARGETWORD#"$PREFIX"} in
		(*:*)
			PREFIX=$PREFIX${${TARGETWORD#"$PREFIX"}%%:*}:
			complete -P "$PREFIX" -g
			;;
		(*)
			complete -T -P "$PREFIX" -S : -u
			;;
		esac
	fi
}
# vim: set ft=sh ts=8 sts=8 sw=8 noet:
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