Make --> optional in markdown command line

Don't enforce the end comment characters --> in markdowns command line. This
closes #2. The new implementation however, enforce that > is not used in
neither the command nor the args.

doxec/__init__.py

@@ -199,19 +199,25 @@ class Markdown(DoxecSyntax):
 
         <!-- COMMAND ARGS -->
 
+        The args part must not contain the greater than '>" character. The
+        trailing '-->' is optional.
         None is returned, if the format does not match. If a valid line is
         found, the tuple (command, args) is returned. 
 
         >>> Markdown.parse_command("<!-- write file.txt -->")
         ('write', 'file.txt')
 
-        >>> Markdown.parse_command("<!-- invalid line ") is None
+        >>> Markdown.parse_command("<!-- write file.txt")
+        ('write', 'file.txt')
+
+        >>> Markdown.parse_command("-- invalid line -->") is None
         True
         """
-        match = re.match(r"<!--\s+(\S.*\S)\s+-->\s*$", line)
+        match = re.match(r"<!--\s+([^> \t\n\r\f\v][^>]*)(\s+-->)?\s*$", line)
         if match is None:
             return None
-        token = re.split("\s+", match.group(1), maxsplit=1)
+
+        token = re.split("\s+", match.group(1).strip(), maxsplit=1)
         if len(token) == 2:
             return tuple(token)
         else:

doxec/tests/markdown.py

@@ -14,6 +14,14 @@ class MarkdownSyntaxTestCase(unittest.TestCase):
         retval = Markdown.parse_command("<!-- WRITE hello_world.c -->")
         self.assertEqual(retval, ("WRITE", "hello_world.c"))
 
+    def test_parse_command_valid_no_end(self):
+        """
+        Run parse_command on an input without the comment end `-->` and check
+        the return value.
+        """
+        retval = Markdown.parse_command("<!-- WRITE hello_world.c")
+        self.assertEqual(retval, ("WRITE", "hello_world.c"))
+
     def test_parse_command_whitespace(self):
         """
         Run parse_command on a valid input with whitespace added/removed in various
@@ -69,6 +77,7 @@ class MarkdownSyntaxTestCase(unittest.TestCase):
         retval = Markdown.parse_command("<! -- WRITE hello_world.c -->")
         self.assertIsNone(retval)
 
+        # this is still invalid, since the args part must not contain '>'
         retval = Markdown.parse_command("<!-- WRITE hello_world.c - ->")
         self.assertIsNone(retval)
 
@@ -83,9 +92,6 @@ class MarkdownSyntaxTestCase(unittest.TestCase):
         retval = Markdown.parse_command("!-- WRITE hello_world.c -->")
         self.assertIsNone(retval)
 
-        retval = Markdown.parse_command("<!-- WRITE hello_world.c ")
-        self.assertIsNone(retval)
-
         retval = Markdown.parse_command("WRITE hello_world.c")
         self.assertIsNone(retval)