[Kdiff3-user] diff/merge algorithm improvements

[<fra...@ce...>]

Hi,

I searched throught the list but did not find a similar question to mine.
The test files are :
a.txt b.txt c.txt
 DEF   DZF   ABC
 GHI   GHI   DEF
             GHI

When I use KDiff3 with:
- a and b, it detects that the first line whas modified : OK.
 a   b
DEF DZF
GHI GHI

- a and c, it detects that a new line was added in c : OK.
 a   c
    ABC
DEF DEF
GHI GHI

- b and c, it detects that  the first line changed and that a new line was
added : it is true, but not optimal.
 b   c
DZF ABC
    DEF
GHI GHI

a more logical diff would be :
 b   c
    ABC
DZF DEF
GHI GHI

- a, b and c : KDiff align DEF(a) with DEF(c) but not with DZF(b), it
aligns DZF(b) with ABC(c), which is not very logic (from a user point of
view). In fact, it would be more accurate if the result was :
 a   b   c
    DZF ABC
DEF     DEF
GHI GHI GHI

a more logical diff would be:
 a   b   c
        ABC
DEF DZF DEF
GHI GHI GHI

We encountered theses behaviours when using the couple
Mercurial(hg)/KDiff3 to manage our source repository. Such "more logical"
or "more smart" diffs would be very useful to merge files.

I think the problem comes from the GNU Diff lib as "vimdiff" (part of
"vim") has the same behaviour. But as you changed the GNU diff lib, if I
submit the problem to the GNU Team, I am not sure the fix (if they do)
will go into KDiff3.

What do you think ? Is it technicaly possible to do such a diff ? Who
should do it (KDiff or GNU) ? Such a diff does not break the "spirit" of
diff/KDiff ?

Have a nice day
François




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