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

[Paul Eggert]

On 01/08/12 10:48, Bruno Haible wrote:

> OK. Can I thus commit the patch that introduces --no-dereference?

Yes, please go ahead.  I'd like to wait for further input
before going ahead with the backwards-incompatible changes to -P,
-H, -L.

> And I don't think many people use these options -P, -H, -L: They are
> undocumented.

The latest version of RCS (5.8) uses diff -L.  I'll file a bug report.
But that's not a good sign.

> --speed-large-files is essential for users who need to reduce
> the running time from O(N²) to O(N).

The running time is O(ND) where D is the number of differences.
One can come up with examples exhibiting O(N**2) behavior, but
they're rare enough in practice that it doesn't seem to be a problem.
As far as I know, --speed-large-files has never been implemented in
GNU diff (as -h was in the original Unix diff); it has always been
a no-op.