add --onchange, fix shellcheck

cdist/conf/type/__sed/gencode-remote

@@ -32,6 +32,7 @@ if ! echo "$script" \
     | diff "$file_from_target" - \
     > /dev/null
 then
+    # shellcheck disable=SC2016
     echo 'tmp="$( mktemp )"'
 
     echo "$sed_cmd -f - '$file' > \"\$tmp\" << EOF"
@@ -41,6 +42,12 @@ then
     echo 'EOF'
 
     echo "cp \"\$tmp\" '$file'"
-    
+
+    # shellcheck disable=SC2016
     echo 'rm -f "$tmp"'
+
+    if [ -f "$__object/parameter/onchange" ]
+    then
+        cat "$__object/parameter/onchange"
+    fi
 fi

cdist/conf/type/__sed/man.rst

@@ -22,6 +22,9 @@ OPTIONAL PARAMETERS
 file
    TODO
 
+onchange
+   TODO
+
 
 BOOLEAN PARAMETERS
 ------------------

cdist/conf/type/__sed/parameter/optional

@@ -1 +1,2 @@
 file
+onchange