shell-completion: fix systemctl set/unset/import-environment

unset-environment is completed with variable names in the environment block.
set-environment the same, but suffixed with "=".
import-environment is completed with variable names in the client environment.

shell-completion/bash/systemctl.in

@@ -320,11 +320,20 @@ _systemctl () {
     elif __contains_word "$verb" ${VERBS[JOBS]}; then
         comps=$( __systemctl $mode list-jobs | { while read -r a b; do echo " $a"; done; } )
 
-    elif __contains_word "$verb" ${VERBS[ENVS]}; then
+    elif [ "$verb" = 'unset-environment' ]; then
+        comps=$( __systemctl $mode show-environment \
+                     | while read -r line; do echo " ${line%%=*}"; done )
+        compopt -o nospace
+
+    elif [ "$verb" = 'set-environment' ]; then
         comps=$( __systemctl $mode show-environment \
                      | while read -r line; do echo " ${line%%=*}="; done )
         compopt -o nospace
 
+    elif [ "$verb" = 'import-environment' ]; then
+        COMPREPLY=( $(compgen -A variable -- "$cur_orig") )
+        return 0
+
     elif __contains_word "$verb" ${VERBS[FILE]}; then
         comps=$( compgen -A file -- "$cur" )
         compopt -o filenames

shell-completion/zsh/_systemctl.in

@@ -365,6 +365,11 @@ for fun in set-environment unset-environment ; do
     }
 done
 
+(( $+functions[_systemctl_import-environment] )) || _systemctl_import-environment()
+{
+    _parameters
+}
+
 (( $+functions[_systemctl_link] )) || _systemctl_link() {
         _sd_unit_files
     }