Subject: bug#21023: [bug-diffutils] bug#21023: REQUEST: --no-dereference missing from manpage + please make a short option for it

From: Jim Meyering <[email-masked]>
Date: Fri, 10 Jul 2015 11:54:37 -0700

On Thu, Jul 9, 2015 at 5:42 PM, Christoph Anton Mitterer
<[email-masked]> wrote:
> It seems that --no-dereference is not documented in the manpage.

Thanks for the report.
However, it is there for me (using diff-3.3), both in "diff --help"
output and in "info diffutils":

   $ diff --help|grep no-d
      --no-dereference            don't follow symbolic links

>From "info diffutils":

  '--no-dereference'
       Act on symbolic links themselves instead of what they point to.

> Apart from that, --no-dereference seem to me like the more native way
> for a recursive diff to work,... i.e. diffing the values of symlinks
> and not (recursively) the stuff they point to.

It's hard to know which way is more intuitive for more people.

> Since no-dereference is so helpful, could you perhaps add a shortcut -R
> that is recursive + no-dereference?

We add short options only very rarely/carefully, because doing so
risks conflicting with usage in other versions of diff.

> Unfortunately it's probably too late to change -r to behave like --no
> -dereference (and instead add a --dereference and a -R).

-P will eventually be a synonym for --no-dereference.
It used to be documented to mean --unidirectional-new-file,
but that was undocumented in 2002.  It is time now to emit
a warning for use of -P, so that we can eventually make it
a synonym for --no-dereference as it is done in numerous
other tools.