--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cmd/completion.go	Wed Apr 19 19:08:47 2017 +0200
@@ -0,0 +1,232 @@
+// Copyright © 2017 Mikael Berthe <mikael@lilotux.net>
+//
+// Licensed under the MIT license.
+// Please see the LICENSE file is this directory.
+
+package cmd
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/spf13/cobra"
+)
+
+var completionCmd = &cobra.Command{
+	Use:       "completion bash|zsh",
+	Short:     "Generate shell completion",
+	ValidArgs: []string{"bash", "zsh"},
+	Run: func(cmd *cobra.Command, args []string) {
+		if len(args) < 1 {
+			errPrint("Please specify your shell")
+			os.Exit(1)
+		}
+
+		switch args[0] {
+		case "bash":
+			if err := runCompletionBash(os.Stdout, RootCmd); err != nil {
+				errPrint("Error: %s", err.Error())
+				os.Exit(1)
+			}
+		case "zsh":
+			if err := runCompletionZsh(os.Stdout, RootCmd); err != nil {
+				errPrint("Error: %s", err.Error())
+				os.Exit(1)
+			}
+		default:
+			errPrint("Only bash is supported at the moment")
+			os.Exit(1)
+		}
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(completionCmd)
+}
+
+func runCompletionBash(out io.Writer, c *cobra.Command) error {
+	return c.GenBashCompletion(out)
+}
+
+// Many thanks to the Kubernetes project for this one!
+func runCompletionZsh(out io.Writer, c *cobra.Command) error {
+	const zshInitialization = `# Copyright 2016 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+__madonctl_bash_source() {
+	alias shopt=':'
+	alias _expand=_bash_expand
+	alias _complete=_bash_comp
+	emulate -L sh
+	setopt kshglob noshglob braceexpand
+
+	source "$@"
+}
+
+__madonctl_type() {
+	# -t is not supported by zsh
+	if [ "$1" == "-t" ]; then
+		shift
+
+		# fake Bash 4 to disable "complete -o nospace". Instead
+		# "compopt +-o nospace" is used in the code to toggle trailing
+		# spaces. We don't support that, but leave trailing spaces on
+		# all the time
+		if [ "$1" = "__madonctl_compopt" ]; then
+			echo builtin
+			return 0
+		fi
+	fi
+	type "$@"
+}
+
+__madonctl_compgen() {
+	local completions w
+	completions=( $(compgen "$@") ) || return $?
+
+	# filter by given word as prefix
+	while [[ "$1" = -* && "$1" != -- ]]; do
+		shift
+		shift
+	done
+	if [[ "$1" == -- ]]; then
+		shift
+	fi
+	for w in "${completions[@]}"; do
+		if [[ "${w}" = "$1"* ]]; then
+			echo "${w}"
+		fi
+	done
+}
+
+__madonctl_compopt() {
+	true # don't do anything. Not supported by bashcompinit in zsh
+}
+
+__madonctl_declare() {
+	if [ "$1" == "-F" ]; then
+		whence -w "$@"
+	else
+		builtin declare "$@"
+	fi
+}
+
+__madonctl_ltrim_colon_completions()
+{
+	if [[ "$1" == *:* && "$COMP_WORDBREAKS" == *:* ]]; then
+		# Remove colon-word prefix from COMPREPLY items
+		local colon_word=${1%${1##*:}}
+		local i=${#COMPREPLY[*]}
+		while [[ $((--i)) -ge 0 ]]; do
+			COMPREPLY[$i]=${COMPREPLY[$i]#"$colon_word"}
+		done
+	fi
+}
+
+__madonctl_get_comp_words_by_ref() {
+	cur="${COMP_WORDS[COMP_CWORD]}"
+	prev="${COMP_WORDS[${COMP_CWORD}-1]}"
+	words=("${COMP_WORDS[@]}")
+	cword=("${COMP_CWORD[@]}")
+}
+
+__madonctl_filedir() {
+	local RET OLD_IFS w qw
+
+	__debug "_filedir $@ cur=$cur"
+	if [[ "$1" = \~* ]]; then
+		# somehow does not work. Maybe, zsh does not call this at all
+		eval echo "$1"
+		return 0
+	fi
+
+	OLD_IFS="$IFS"
+	IFS=$'\n'
+	if [ "$1" = "-d" ]; then
+		shift
+		RET=( $(compgen -d) )
+	else
+		RET=( $(compgen -f) )
+	fi
+	IFS="$OLD_IFS"
+
+	IFS="," __debug "RET=${RET[@]} len=${#RET[@]}"
+
+	for w in ${RET[@]}; do
+		if [[ ! "${w}" = "${cur}"* ]]; then
+			continue
+		fi
+		if eval "[[ \"\${w}\" = *.$1 || -d \"\${w}\" ]]"; then
+			qw="$(__madonctl_quote "${w}")"
+			if [ -d "${w}" ]; then
+				COMPREPLY+=("${qw}/")
+			else
+				COMPREPLY+=("${qw}")
+			fi
+		fi
+	done
+}
+
+__madonctl_quote() {
+    if [[ $1 == \'* || $1 == \"* ]]; then
+        # Leave out first character
+        printf %q "${1:1}"
+    else
+        printf %q "$1"
+    fi
+}
+
+autoload -U +X bashcompinit && bashcompinit
+
+# use word boundary patterns for BSD or GNU sed
+LWORD='[[:<:]]'
+RWORD='[[:>:]]'
+if sed --help 2>&1 | grep -q GNU; then
+	LWORD='\<'
+	RWORD='\>'
+fi
+
+__madonctl_convert_bash_to_zsh() {
+	sed \
+	-e 's/declare -F/whence -w/' \
+	-e 's/local \([a-zA-Z0-9_]*\)=/local \1; \1=/' \
+	-e 's/flags+=("\(--.*\)=")/flags+=("\1"); two_word_flags+=("\1")/' \
+	-e 's/must_have_one_flag+=("\(--.*\)=")/must_have_one_flag+=("\1")/' \
+	-e "s/${LWORD}_filedir${RWORD}/__madonctl_filedir/g" \
+	-e "s/${LWORD}_get_comp_words_by_ref${RWORD}/__madonctl_get_comp_words_by_ref/g" \
+	-e "s/${LWORD}__ltrim_colon_completions${RWORD}/__madonctl_ltrim_colon_completions/g" \
+	-e "s/${LWORD}compgen${RWORD}/__madonctl_compgen/g" \
+	-e "s/${LWORD}compopt${RWORD}/__madonctl_compopt/g" \
+	-e "s/${LWORD}declare${RWORD}/__madonctl_declare/g" \
+	-e "s/\\\$(type${RWORD}/\$(__madonctl_type/g" \
+	<<'BASH_COMPLETION_EOF'
+`
+
+	const zshTail = `
+BASH_COMPLETION_EOF
+}
+
+__madonctl_bash_source <(__madonctl_convert_bash_to_zsh)
+`
+
+	buf := new(bytes.Buffer)
+	out.Write([]byte(zshInitialization))
+	err := c.GenBashCompletion(buf)
+	script := strings.Replace(buf.String(), "flaghash[${flagname}]", `flaghash[workaround]`, -1)
+	out.Write([]byte(script))
+	out.Write([]byte(zshTail))
+	return err
+}