--- a/cutils/treesum.py	Mon Mar 10 01:57:25 2025 +0100
+++ b/cutils/treesum.py	Mon Mar 10 10:04:02 2025 +0100
@@ -747,9 +747,18 @@
                     else:
                         opath = walk.WalkDirEntry.alt_fs(opath)
                     if eno == 0:
+                        #
+                        # treesum file could be read.
+                        # Now check whether the infos we got from it are
+                        # compatible with our current requirements
+                        # (digest, size).
+                        #
                         if self._size_only:
                             if collector.size is None:
-                                # This is a severe error here
+                                #
+                                # This is a severe error here: just the size
+                                # is required, but we have not got one.
+                                #
                                 self._writer.write_error(util.b(
                                     util.interpolate_bytes(
                                         "No size in treesum-file `%s' while"
@@ -776,7 +785,11 @@
                             else:
                                 sz = None
                             if collector.digest is None:
-                                # This is really a severe error
+                                #
+                                # This is really a severe error. Most probably
+                                # the treesum file was created with
+                                # "--size-only" and contains no digest.
+                                #
                                 self._writer.write_error(util.b(
                                     util.interpolate_bytes(
                                         "No digest in treesum-file `%s' while"
@@ -790,6 +803,7 @@
                                     use_base64=self._use_base64,
                                     size=sz)
                                 return (errno.ESRCH, None, None, None)
+                        # We got all required infos without errors
                         if self._size_only:
                             self._writer.write_size(opath, collector.size)
                         else:
@@ -801,6 +815,9 @@
                                 collector.digest,
                                 collector.size)
                     else:
+                        #
+                        # treesum file could not be read
+                        #
                         self._writer.write_error(util.interpolate_bytes(
                             "Cannot read treesum-file `%s' for directory"
                             "`%s': %s",
@@ -814,6 +831,9 @@
                                 self._algorithm[1], opath, None,
                                 use_base64=self._use_base64, size=None)
                         return (eno, None, None, None)
+        #
+        # No treesum file: just process normally with digesting
+        #
         if self._utf8_mode:
             fsobjects.sort(key=walk.WalkDirEntry.sort_key_u8)
         else: