bug#40352: cp -a --attributes-only zeroes a file with more than one link

[Matt Kloss]

   Hello,

   When you cp -a --attributes-only a file which has a more than one
   “hardlink”, it zeroes the file:



   $ echo hello > aaa

   $ cp aaa foo

   $ chmod 777 aaa

   $ ls -li

   total 8

   407584 -rwxrwxrwx 1 matt matt 6 mars  31 14:19 aaa

   399313 -rw-r--r-- 1 matt matt 6 mars  31 14:19 foo

   $ cp -a --attributes-only aaa foo   # this is fine

   $ ls -li

   total 8

   407584 -rwxrwxrwx 1 matt matt 6 mars  31 14:19 aaa

   399313 -rwxrwxrwx 1 matt matt 6 mars  31 14:19 foo

   $ ln foo foo2

   $ cp -a --attributes-only aaa foo   # here comes the bug

   $ ls -li

   total 8

   407584 -rwxrwxrwx 1 matt matt 6 mars  31 14:19 aaa

   407740 -rwxrwxrwx 1 matt matt 0 mars  31 14:19 foo

   399313 -rwxrwxrwx 1 matt matt 6 mars  31 14:19 foo2



   foo has a size of 0 bytes!

   The user thinks he's replicating timestamp and permissions, and he's
   actually deleting data. (Well, the data is still in foo2, but...)



   coreutils 8.30



   Matt