Re: [bug-diffutils] diff: support for --no-dereference option

[Bruno Haible]

Andreas Gruenbacher wrote:
> I wonder if comparing symlinks (instead of what they point to) shouldn't
> become the default once diff supports it.  At the very least, diff
> should warn when following symlinks though.

I disagree. --dereference should stay the default, for two reasons:

  1) Unix philosophy: By default, symlinks are followed. This is a
     general principle. It starts with open() and fopen() and continues
     through most command-line utilities.

  2) What are the use-cases for "diff"?
       - Compare files coming from two different users.
       - Comparing the new state of a directory with a backup.
       - Compating the new state of a partition with a backup.

     In the first two cases, --dereference is desired. In the third case,
     --no-dereference is desired.

     The first two cases are the most frequent ones.

     In other words, while you personally may be working frequently at
     the partition level, many users who put a symbolic link want it to be
     followed automatically.

See also the discussion at
<https://lists.gnu.org/archive/html/bug-gnu-utils/2011-10/msg00011.html>
<https://lists.gnu.org/archive/html/bug-gnu-utils/2011-10/msg00013.html>

Bruno