fix: don't double join path for dockerfile

All code paths up to here already join the context path and with the check above
we're sure the file exists so joining again leads to paths that don't exist

Signed-off-by: Dominik Süß <dominik@suess.wtf>

Author: theSuess

podman_compose.py

@@ -2917,7 +2917,7 @@ def cleanup_temp_dockfile() -> None:
 
         if path_exists(dockerfile):
             # normalize dockerfile path, as the user could have provided unpredictable file formats
-            dockerfile = os.path.normpath(os.path.join(ctx, dockerfile))
+            dockerfile = os.path.normpath(dockerfile)
             build_args.extend(["-f", dockerfile])
         else:
             if custom_dockerfile_given:

tests/unit/test_container_to_build_args.py

@@ -352,3 +352,23 @@ def test_build_ssh_array(self):
                 '.',
             ],
         )
+
+    def test_containerfile_in_context(self):
+        c = create_compose_mock()
+
+        cnt = get_minimal_container()
+        cnt['build']['context'] = "./subdir"
+        args = get_minimal_args()
+        args = container_to_build_args(c, cnt, args, lambda path: True)
+        self.assertEqual(
+            args,
+            [
+                '-f',
+                'subdir/Containerfile',
+                '-t',
+                'new-image',
+                '--no-cache',
+                '--pull-always',
+                './subdir',
+            ],
+        )