Fixes #241 - reorder tar adds so dirs are last

This doesn't address mtimes, but then neither did the original
version.

Thanks to Richard Maw for identifying the root cause, explaining
how to fix, and reviewing the code.

ybd/utils.py

@@ -23,7 +23,6 @@
 from fs.osfs import OSFS
 from fs.multifs import MultiFS
 import calendar
-
 import app
 
 # The magic number for timestamps: 2011-11-11 11:11:11
@@ -343,22 +342,28 @@ def add_directory_to_tarfile(f_tar, dir_name, dir_arcname):
                 add_directory_to_tarfile(f_tar, root_dir, '.')
 
 
-def make_deterministic_tar_archive(base_name, root_dir):
+def make_deterministic_tar_archive(base_name, root):
     '''Make a tar archive of contents of 'root_dir'.
 
-    This function uses monkeypatching to make shutil.make_archive() create
-    a deterministic tarfile.
+    This function takes extra steps to make the output more deterministic,
+    compared to shutil.make_archive() - it sorts the results to ensure
+    the ordering of the files in the archive is always the same.
 
-    https://bugs.python.org/issue24465 will make this function redundant.
+    Also this puts the directory last, to workaround a bug in docker/overlayfs
+    runners - see https://gitlab.com/baserock/ybd/issues/241
 
-    '''
-    real_listdir = os.listdir
+    FIXME: make this do timestamps
 
-    def stable_listdir(path):
-        return sorted(real_listdir(path))
+    '''
 
-    with monkeypatch(os, 'listdir', stable_listdir):
-        shutil.make_archive(base_name, 'tar', root_dir)
+    with app.chdir(root), open(base_name + '.tar', 'wb') as f:
+        with tarfile.TarFile(mode='w', fileobj=f) as f_tar:
+            directories = [d[0] for d in os.walk('.')]
+            for d in sorted(directories):
+                files = [os.path.join(d, f) for f in os.listdir(d)]
+                for path in sorted(files):
+                    f_tar.add(name=path, recursive=False)
+                f_tar.add(name=d, recursive=False)
 
 
 def _find_extensions(paths):