bash-completion: --property support

Just bash.

shell-completion/bash/systemctl

@@ -22,6 +22,15 @@ __systemctl() {
         systemctl $mode --full --no-legend "$@"
 }
 
+__systemd_properties() {
+        local mode=$1
+        { __systemctl $mode show;
+         systemd --dump-configuration-items; } |
+        while IFS='=' read -r key value; do
+            [[ $value ]] && echo "$key"
+        done
+}
+
 __contains_word () {
         local word=$1; shift
         for w in $*; do [[ $w = $word ]] && return 0; done
@@ -67,6 +76,12 @@ _systemctl () {
                       [ARG]='--host -H --kill-mode --kill-who --property -p --signal -s --type -t --root'
         )
 
+        if __contains_word "--user" ${COMP_WORDS[*]}; then
+            mode=--user
+        else
+            mode=--system
+        fi
+
         if __contains_word "$prev" ${OPTS[ARG]}; then
                 case $prev in
                         --signal|-s)
@@ -89,7 +104,7 @@ _systemctl () {
                                 comps=$(compgen -A hostname)
                         ;;
                         --property|-p)
-                                comps=''
+                                comps=$(__systemd_properties $mode)
                         ;;
                 esac
                 COMPREPLY=( $(compgen -W '$comps' -- "$cur") )
@@ -101,12 +116,6 @@ _systemctl () {
                 return 0
         fi
 
-        if __contains_word "--user" ${COMP_WORDS[*]}; then
-            mode=--user
-        else
-            mode=--system
-        fi
-
         local -A VERBS=(
                 [ALL_UNITS]='is-active is-failed is-enabled status show mask preset'
             [ENABLED_UNITS]='disable'