util: Retry resolving git branches

When there's a temporary network issue, Pungi will fail to turn a branch
into a commit hash. This would abort the whole compose. Instead we
should just retry a few times.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

pungi/util.py

@@ -253,7 +253,7 @@ def resolve_git_url(url):
     scheme = r.scheme.replace('git+', '')
 
     baseurl = urlparse.urlunsplit((scheme, r.netloc, r.path, '', ''))
-    _, output = run(['git', 'ls-remote', baseurl, ref])
+    _, output = git_ls_remote(baseurl, ref)
 
     lines = [line for line in output.split('\n') if line]
     if len(lines) == 0:
@@ -776,3 +776,8 @@ def retry(timeout=120, interval=30, wait_on=Exception):
                     time.sleep(interval)
         return inner
     return wrapper
+
+
+@retry(wait_on=RuntimeError)
+def git_ls_remote(baseurl, ref):
+    return run(['git', 'ls-remote', baseurl, ref])

tests/test_util.py

@@ -92,6 +92,18 @@ class TestGitRefResolver(unittest.TestCase):
             ['git', 'ls-remote', 'https://git.example.com/repo.git', 'refs/heads/my-branch'])
         self.assertIn('ref does not exist in remote repo', str(ctx.exception))
 
+    @mock.patch('time.sleep')
+    @mock.patch('pungi.util.run')
+    def test_retry(self, run, sleep):
+        run.side_effect = [RuntimeError('Boom'), (0, 'CAFEBABE\tHEAD\n')]
+
+        url = util.resolve_git_url('https://git.example.com/repo.git?somedir#HEAD')
+
+        self.assertEqual(url, 'https://git.example.com/repo.git?somedir#CAFEBABE')
+        self.assertEqual(sleep.call_args_list, [mock.call(30)])
+        self.assertEqual(run.call_args_list,
+                         [mock.call(['git', 'ls-remote', 'https://git.example.com/repo.git', 'HEAD'])] * 2)
+
 
 class TestGetVariantData(unittest.TestCase):
     def test_get_simple(self):