Subject: bug#61537: [Bug-coreutils] 'cp -au' re-copies (removes and relinks) hard links that are up to date

From: Antonio Diaz Diaz <[email-masked]>
Date: Wed, 15 Feb 2023 19:58:22 +0100

Hello.

I have been forced recently to update my coreutils 8.11 (because 'touch' in 
8.11 didn't understand the dates with a 'T' separator passed to it by the 
configure of another GNU package I was installing) and have found that 'cp 
-au' now re-copies (removes and relinks) hard links that are up to date and 
it didn't recopy with 8.11.

I have tried coreutils 8.23 and 9.1, but I think all versions after 8.11 
have this problem.

To illustrate the problem, I first create a directory 'src' containing two 
linked files and then make a copy of 'src' in 'dest':

$ md src
$ echo "foo" > src/a
$ ln src/a src/b
$ cp -auv src dest
'src' -> 'dest'
'src/a' -> 'dest/a'
'src/b' -> 'dest/b'

Now, every time I update 'dest' using 'cp -au', it removes and relinks 
'dest/b' in spite of it already being a link to 'dest/a':

$ cp -auv src/* dest
removed 'dest/b'

But with 'cp' from coreutils 8.11, 'dest/b' was not recopied:

$ /tmp/coreutils-8.11/src/cp -auv src/* dest
$

Can current 'cp' be fixed so that it notices that the destination is already 
updated, and thus avoids removing and relinking it, just as it did in 
coreutils 8.11?

Thanks,
Antonio.