Tools: add --fresh-params option to sim_vehicle.py

This will rebuild and use the XML file we generate from our
source code which conveys information about our parameters.

When using this option, "param help PARAMETERNAME" should reflect
changes made to the parameter metadata for PARAMETERNAME.

Tools/autotest/sim_vehicle.py

@@ -350,6 +350,20 @@ def do_build_waf(opts, frame_options):
     os.chdir(old_dir)
 
 
+def do_build_parameters(vehicle):
+    # build succeeded
+    # now build parameters
+    progress("Building fresh parameter descriptions")
+    param_parse_path = os.path.join(
+        find_root_dir(), "Tools/autotest/param_metadata/param_parse.py")
+    cmd_param_build = ["python", param_parse_path, '--vehicle', vehicle]
+
+    _, sts = run_cmd_blocking("Building fresh params", cmd_param_build)
+    if sts != 0:
+        progress("Parameter build failed")
+        sys.exit(1)
+
+
 def do_build(vehicledir, opts, frame_options):
     """Build build target (e.g. sitl) in directory vehicledir"""
 
@@ -617,6 +631,11 @@ def start_mavproxy(opts, stuff):
     if opts.aircraft is not None:
         cmd.extend(['--aircraft', opts.aircraft])
 
+    if opts.fresh_params:
+        # these were built earlier:
+        path = os.path.join(os.getcwd(), "apm.pdef.xml")
+        cmd.extend(['--load-module', 'param:{"xml-filepath":"%s"}' % path])
+
     if len(extra_cmd):
         cmd.extend(['--cmd', extra_cmd])
 
@@ -798,6 +817,11 @@ group_sim.add_option("", "--no-mavproxy",
                      action='store_true',
                      default=False,
                      help="Don't launch MAVProxy")
+group_sim.add_option("", "--fresh-params",
+                     action='store_true',
+                     dest='fresh_params',
+                     default=False,
+                     help="Generate and use local parameter help XML")
 parser.add_option_group(group_sim)
 
 
@@ -948,6 +972,9 @@ else:
     if not cmd_opts.no_rebuild:  # i.e. we should rebuild
         do_build(vehicle_dir, cmd_opts, frame_infos)
 
+    if cmd_opts.fresh_params:
+        do_build_parameters(cmd_opts.vehicle)
+
     if cmd_opts.build_system == "waf":
         if cmd_opts.debug:
             binary_basedir = "build/sitl-debug"