Support comma-separated values for --image-format option

As documented in the command line help message.

Signed-off-by: Gaëtan Lehmann <gaetan.lehmann@vates.tech>

Author: glehmann

conftest.py

@@ -2,6 +2,7 @@
 
 import pytest
 
+import argparse
 import itertools
 import logging
 import os
@@ -50,6 +51,15 @@
     CACHE_IMPORTED_VM = False
 assert CACHE_IMPORTED_VM in [True, False]
 
+class SplitCommaAction(argparse.Action):
+    def __call__(self, parser, namespace, values, option_string=None):
+        items = getattr(namespace, self.dest, None)
+        if items is None:
+            items = []
+        if isinstance(values, str):
+            items.extend([v.strip() for v in values.split(",") if v.strip()])
+        setattr(namespace, self.dest, items)
+
 # pytest hooks
 
 def pytest_addoption(parser: pytest.Parser) -> None:
@@ -99,7 +109,7 @@ def pytest_addoption(parser: pytest.Parser) -> None:
     )
     parser.addoption(
         "--image-format",
-        action="append",
+        action=SplitCommaAction,
         default=[],
         help="Format of VDI to execute tests on."
         "Example: vhd,qcow2"