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.

osbuild/util/path.py

@@ -1,5 +1,36 @@
 """Path handling utility functions"""
+import errno
 import os
+import os.path
+from typing import Optional
+
+from .ctx import suppress_oserror
+
+
+def clamp_mtime(path: str, start: int, to: int):
+    """Clamp all modification times of 'path'
+
+    Set the mtime of 'path' to 'to' if it is greater or equal to 'start'.
+    If 'to' is None, the mtime is set to the current time.
+    """
+
+    times = (to, to)
+
+    def fix_utime(path, dfd: Optional[int] = None):
+        sb = os.stat(path, dir_fd=dfd, follow_symlinks=False)
+        if sb.st_mtime < start:
+            return
+
+        # We might get a permission error when the immutable flag is set;
+        # since there is nothing much we can do, we just ignore it
+        with suppress_oserror(errno.EPERM):
+            os.utime(path, times, dir_fd=dfd, follow_symlinks=False)
+
+    fix_utime(path)
+
+    for _, dirs, files, dfd in os.fwalk(path):
+        for f in dirs + files:
+            fix_utime(f, dfd)
 
 
 def in_tree(path: str, tree: str, must_exist: bool = False) -> bool:

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