util/path: new clamp mtime function

New utility function to clamp all mtimes of a given path to a
certain timestamp. Clamp here means that any timestamp later
than the specified upper bound will be set to the upper bound.

test/mod/test_util_path.py

@@ -2,10 +2,54 @@
 # Tests for the 'osbuild.util.path' module
 #
 import os
+import time
+from pathlib import Path
+from tempfile import TemporaryDirectory
+
+import pytest
 
 from osbuild.util import path
 
 
+@pytest.fixture(name="tempdir")
+def tempdir_fixture():
+    with TemporaryDirectory(prefix="path-") as tmp:
+        yield tmp
+
+
+def test_clamp_mtime(tempdir):
+    start = int(time.time())
+
+    tree = Path(tempdir, "tree")
+    tree.mkdir()
+    os.makedirs(os.path.join(tree, "a", "bunch", "of", "directories"))
+
+    file = Path(tree, "file")
+    file.touch()
+
+    folder = Path(tree, "folder")
+    folder.mkdir()
+
+    link = Path(tree, "link")
+    link.symlink_to(folder, target_is_directory=True)
+
+    timepoint = 1644758228
+    path.clamp_mtime(tree, start, timepoint)
+
+    def ensure_mtime(target, dfd):
+        stat = os.stat(target, dir_fd=dfd, follow_symlinks=False)
+        assert stat.st_mtime <= timepoint
+
+    for _, dirs, files, dfd in os.fwalk(tree):
+        ensure_mtime(".", dfd)
+
+        for d in dirs:
+            ensure_mtime(d, dfd)
+
+        for f in files:
+            ensure_mtime(f, dfd)
+
+
 def test_in_tree():
     cases = {
         ("/tmp/file", "/tmp", False): True,  # Simple, non-existent