ostree: show commit metadata

This new API call allows one to check (among other things) if a commit
exists in a repo. It'll throw a RuntimeException if the commit is
missing.

osbuild/util/ostree.py

@@ -129,6 +129,24 @@ def rev_parse(repo: PathLike, ref: str) -> str:
     return msg
 
 
+def show(repo: PathLike, checksum: str) -> str:
+    """Show the metada of an OSTree object pointed by `checksum` in the repository at `repo`"""
+
+    repo = os.fspath(repo)
+
+    r = subprocess.run(["ostree", "show", f"--repo={repo}", checksum],
+                       encoding="utf-8",
+                       stdout=subprocess.PIPE,
+                       stderr=subprocess.STDOUT,
+                       check=False)
+
+    msg = r.stdout.strip()
+    if r.returncode != 0:
+        raise RuntimeError(msg)
+
+    return msg
+
+
 def deployment_path(root: PathLike, osname: str, ref: str, serial: int):
     """Return the path to a deployment given the parameters"""
 

test/mod/test_util_ostree.py

@@ -8,6 +8,7 @@ import os
 import subprocess
 import tempfile
 import unittest
+import pytest
 
 from osbuild.util import ostree
 
@@ -22,7 +23,7 @@ def run(*args, check=True, encoding="utf-8", **kwargs):
     return res
 
 
-class TestObjectStore(unittest.TestCase):
+class TestObjectStore(test.TestBase):
 
     # pylint: disable=no-self-use
     @unittest.skipUnless(test.TestBase.have_rpm_ostree(), "rpm-ostree missing")
@@ -88,6 +89,13 @@ class TestObjectStore(unittest.TestCase):
         for p, v in params.items():
             self.assertEqual(v, js[p])
 
+    @unittest.skipUnless(test.TestBase.have_test_data(), "no test-data access")
+    def test_show_commit(self):
+        repo_path = os.path.join(self.locate_test_data(), "sources/org.osbuild.ostree/data/repo")
+        ostree.show(repo_path, "d6243b0d0ca3dc2aaef2e0eb3e9f1f4836512c2921007f124b285f7c466464d8")
+        with pytest.raises(RuntimeError):
+            ostree.show(repo_path, "f000000000000000000000000DEADBEEF000000000000000000000000000000f")
+
 
 class TestPasswdLike(unittest.TestCase):