builder: make repo a proper optional argument

When the builder is used as an command line binary: have `repo`
be a proper command line argument. It was currently specified
before arch which can be passed multiple times, but so does
repo; hence one of them needs to be optional.

plugins/builder/osbuild.py

@@ -551,10 +551,10 @@ def main():
     subpar.add_argument("version", metavar="VERSION", help='The version')
     subpar.add_argument("release", metavar="RELEASE", help='The release')
     subpar.add_argument("distro", metavar="DISTRO", help='The distribution')
-    subpar.add_argument("repo", metavar="REPO", help='The repository to use',
-                        type=str, action="append", default=[])
     subpar.add_argument("arch", metavar="ARCHITECTURE", help='Request the architecture',
                         type=str, nargs="+")
+    subpar.add_argument("--repo", metavar="REPO", help='The repository to use',
+                        type=str, action="append", default=[])
     subpar.add_argument("--format", metavar="FORMAT", help='Request the image format [qcow2]',
                         action="append", type=str, default=[])
     subpar.add_argument("--koji", metavar="URL", help='The koji url',

test/unit/test_builder.py

@@ -645,8 +645,8 @@ class TestBuilderPlugin(PluginTest):
             "33",
             "20201015.0",
             "fedora-33",
-            "http://download.localhost/pub/linux/$arch",
             "x86_64",
+            "--repo", "http://download.localhost/pub/linux/$arch",
             "--cert", ", ".join(certs),
             "--ca", "test/data/example-ca.pem"
         ]