[Kdiff3-user] Comparing partially hardlinked trees

[Bruno <bon...@in...>]

KDiff3 is very slow to compare two (or 3) directory trees where most of the 
files are hardlinked between the trees.
KDiff3 should detect such hardlinks and skip content comparison in such cases 
as diff does.

Sample tree setup (only the first level shown)

linux.orig/                   linux.mine/
  arch/                         arch/
  COPYING         <hardlink>    COPYING
  crypto/                       crypto/
  drivers/                      driver/
  include/                      include/
  ipc/                          ipc/
  kernel/                       kernel/
  MAINTAINERS     <hardlink>    MAINTAINERS
  mm/                           mm/
  README          <hardlink>    README
  scripts/                      scripts/
  sound/                        sound/
  block/                        block/
  CREDITS         <hardlink>    CREDITS
  Documentation/                Documentation/
  fs/                           fs/
  init/                         init/
  Kbuild          <hardlink>    Kbuild
  lib/                          lib/
  Makefile                      Makefile           (different)
  net/                          net/
  REPORTING-BUGS  <hardlink>    REPORTING-BUGS
  security/                     security/
  usr/                          usr/

As you can see all files which are equal are hardlinked together.
When comparing two files kdiff3 should first check if the files are on same 
device and have same inode; if so mark files as equal WITHOUT looking at the 
content, otherwise proceed as usual.
Without such a check it takes an eternity to compare two trees as big as 
kernel tree with only a few changes...

Regards,
Bruno