18.1.2 Handling Changes to the Directory Structure

diff and patch do not handle some changes to directory structure. For example, suppose one directory tree contains a directory named ‘D’ with some subsidiary files, and another contains a file with the same name ‘D’. ‘diff -r’ does not output enough information for patch to transform the directory subtree into the file.

There should be a way to specify that a file has been removed without having to include its entire contents in the patch file. There should also be a way to tell patch that a file was renamed, even if there is no way for diff to generate such information. There should be a way to tell patch that a file's time stamp has changed, even if its contents have not changed.

These problems can be fixed by extending the diff output format to represent changes in directory structure, and extending patch to understand these extensions.