Fix duplicated commands in Message.command

Also add more test cases
Related to #676

pyrogram/filters.py

@@ -789,7 +789,7 @@ def command(commands: Union[str, List[str]], prefixes: Union[str, List[str]] = "
                                 flags=re.IGNORECASE if not flt.case_sensitive else 0):
                     continue
 
-                without_command = re.sub(rf"{cmd}(?:@?{username})?\s", "", without_prefix, count=1)
+                without_command = re.sub(rf"{cmd}(?:@?{username})?\s?", "", without_prefix, count=1)
 
                 # match.groups are 1-indexed, group(1) is the quote, group(2) is the text
                 # between the quotes, group(3) is unquoted, whitespace-split text

tests/filters/test_command.py

@@ -103,6 +103,14 @@ async def test_with_mention():
 async def test_with_args():
     f = filters.command("start")
 
+    m = Message("/start")
+    await f(c, m)
+    assert m.command == ["start"]
+
+    m = Message("/start@username")
+    await f(c, m)
+    assert m.command == ["start"]
+
     m = Message("/start a b c")
     await f(c, m)
     assert m.command == ["start"] + list("abc")