add --onchange to __line

cdist/conf/type/__line/gencode-remote

@@ -122,3 +122,7 @@ END {
 ' "$file" > "\$tmpfile"
 mv -f "\$tmpfile" "$file"
 DONE
+
+if [ -f "$__object/parameter/onchange" ]; then
+   cat "$__object/parameter/onchange"
+fi

cdist/conf/type/__line/man.rst

@@ -46,6 +46,8 @@ regex
 state
     'present' or 'absent', defaults to 'present'
 
+onchange
+    The code to run if line is added, removed or updated.
 
 
 BOOLEAN PARAMETERS

cdist/conf/type/__line/parameter/optional

@@ -4,3 +4,4 @@ file
 line
 regex
 state
+onchange