check for gcode comments that contain controller-specific commands to include

src/Mod/Path/PathScripts/post/grbl_post.py

@@ -31,6 +31,7 @@ import argparse
 import datetime
 import shlex
 import PathScripts.PathUtil as PathUtil
+import regex
 
 
 TOOLTIP = """
@@ -578,6 +579,12 @@ def parse(pathobj):
             if len(outstring) >= 1:
                 out += linenumber() + format_outstring(outstring) + "\n"
 
+            # Check for comments containing machine-specific commands to pass literally to the controller
+            m = regex.match(r'^\(MC_RUN_COMMAND: ([^)]+)\)$', command)
+            if m:
+                raw_command = m.group(1)
+                out += linenumber() + raw_command + "\n"
+
     return out