/usr/share/bash-completion/completions/fwupdmgr is in fwupd 1.0.6-2.
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 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 | _fwupdmgr_cmd_list=(
	'build-firmware'
	'clear-history'
	'clear-offline'
	'clear-results'
	'downgrade'
	'get-details'
	'get-devices'
	'get-history'
	'get-releases'
	'get-remotes'
	'get-results'
	'get-updates'
	'hwids'
	'install'
	'install-prepared'
	'modify-remote'
	'monitor'
	'refresh'
	'report-history'
	'smbios-dump'
	'unlock'
	'update'
	'verify'
	'verify-update'
	'--version'
)
_fwupdmgr_opts=(
	'--verbose'
	'--offline'
	'--allow-reinstall'
	'--allow-older'
	'--force'
	'--assume-yes'
	'--no-unreported-check'
	'--no-metadata-check'
	'--no-reboot-check'
)
_show_modifiers()
{
	COMPREPLY+=( $(compgen -W '${_fwupdmgr_opts[@]}' -- "$cur") )
}
_show_device_ids()
{
	local description
	OLDIFS=$IFS
	IFS=$'\n'
	description="$(command fwupdmgr get-devices | command awk '!/DeviceId/ { line = $0 }; /DeviceId/ { print $2 " {" line "}"}')"
	COMPREPLY+=( $(compgen -W "${description}" -- "$cur") )
	IFS=$OLDIFS
}
_show_remotes()
{
	local remotes
	remotes="$(command fwupdmgr get-remotes | command awk '/Remote ID/ { print $3 }')"
	COMPREPLY+=( $(compgen -W "${remotes}" -- "$cur") )
}
_fwupdmgr()
{
	local cur prev command
	COMPREPLY=()
	cur=`_get_cword`
	prev=${COMP_WORDS[COMP_CWORD-1]}
	command=${COMP_WORDS[1]}
	case $command in
	clear-results|downgrade|get-releases|get-results|unlock|verify|verify-update)
		if [[ "$prev" = "$command" ]]; then
			_show_device_ids
		else
			_show_modifiers
		fi
		;;
	get-details|smbios-dump)
		#browse for file
		if [[ "$prev" = "$command" ]]; then
			_filedir
		#modifiers
		else
			_show_modifiers
		fi
		;;
	install)
		#find files
		if [[ "$prev" = "$command" ]]; then
			_filedir
		#device ID or modifiers
		elif [[ "$prev" = "${COMP_WORDS[2]}" ]]; then
			_show_device_ids
			_show_modifiers
		#modifiers
		else
			_show_modifiers
		fi
		;;
	modify-remote)
		#find remotes
		if [[ "$prev" = "$command" ]]; then
			_show_remotes
		#add key
		elif [[ "$prev" = "${COMP_WORDS[2]}" ]]; then
			local keys
			keys="$(command fwupdmgr get-remotes | command awk -v pattern="Remote ID:.*${prev}$" '$0~pattern{show=1; next}/Remote/{show=0}{gsub(/:.*/,"")}show')"
			COMPREPLY+=( $(compgen -W "${keys}" -- "$cur") )
		fi
		;;
	refresh)
		#find first file
		if [[ "$prev" = "$command" ]]; then
			_filedir
		#find second file
		elif [[ "$prev" = "${COMP_WORDS[2]}" ]]; then
			_filedir
		#find remote ID
		elif [[ "$prev" = "${COMP_WORDS[3]}" ]]; then
			_show_remotes
		else
			_show_modifiers
		fi
		;;
	build-firmware)
		#file in
		if [[ "$prev" = "$command" ]]; then
			_filedir
		#file out
		elif [[ "$prev" = "${COMP_WORDS[2]}" ]]; then
			_filedir
		#script
		elif [[ "$prev" = "${COMP_WORDS[3]}" ]]; then
			_filedir
		#output
		elif [[ "$prev" = "${COMP_WORDS[4]}" ]]; then
			_filedir
		else
			_show_modifiers
		fi
		;;
	*)
		#find first command
		if [[ ${COMP_CWORD} = 1 ]]; then
			COMPREPLY=( $(compgen -W '${_fwupdmgr_cmd_list[@]}' -- "$cur") )
		#modifiers for all commands
		else
			_show_modifiers
		fi
		;;
	esac
	return 0
}
complete -F _fwupdmgr fwupdmgr
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