stages/tar: add --numeric-owner option

The numeric-owner option omits the inclusion of user and group names in
the archive metadata.  This is often desirable since name and group
mappings can change the ownership of files during extraction.

The test uses the tarfile module to check that the uname and gname
attributes in the tar archive itself are empty, which is the intended
effect of enabling numeric-owner [1].

RHEL-102854

[1] https://www.gnu.org/software/tar//manual/html_section/Attributes.html

stages/org.osbuild.tar

@@ -37,6 +37,9 @@ def main(inputs, output_dir, options):
     if transform:
         extra_args += ["--transform", transform]
 
+    if options.get("numeric-owner", False):
+        extra_args += ["--numeric-owner"]
+
     compression = options.get("compression", "auto")
 
     if compression == "auto":

stages/org.osbuild.tar.meta.json

@@ -113,6 +113,10 @@
         "transform": {
           "type": "string",
           "description": "Used to transform filenames and directly passed to --transform"
+        },
+        "numeric-owner": {
+          "type": "boolean",
+          "description": "Always use numbers for user/group names"
         }
       }
     },

stages/test/test_tar.py

@@ -3,6 +3,7 @@
 import os.path
 import re
 import subprocess
+import tarfile
 
 import pytest
 
@@ -190,3 +191,24 @@ def test_tar_compress(tmp_path, stage_module, fake_inputs, filename, compression
     assert os.path.exists(tar_path)
     output = subprocess.check_output(["file", tar_path], encoding="utf-8")
     assert expected in output.lower()
+
+
+@pytest.mark.skipif(not has_executable("tar"), reason="no tar executable")
+@pytest.mark.parametrize("numeric_owner", [True, False,])
+def test_tar_numeric_owner(tmp_path, stage_module, fake_inputs, numeric_owner):
+    options = {
+        "filename": "out.tar",
+        "numeric-owner": numeric_owner,
+    }
+    stage_module.main(fake_inputs, tmp_path, options)
+
+    tar_path = os.path.join(tmp_path, "out.tar")
+    assert os.path.exists(tar_path)
+
+    # read the tar archive directly instead of relying on parsing the human-readable verbose output
+    with tarfile.open(tar_path, mode="r") as archive:
+        for item in archive.getmembers():
+            # when enabling numeric-owner, the uname and gname fields are empty
+            info = item.get_info()
+            assert (info["uname"] == "") == numeric_owner
+            assert (info["gname"] == "") == numeric_owner