Hi,
On Thu, 8 Jan 2009, Sam Vilain wrote:
> On Tue, 2009-01-06 at 20:40 +0100, Johannes Schindelin wrote:
> > Although I would like to see it in once it is fleshed out -- even if it
> > does not meet our usefulness standard -- because people said Git is
> > inferior for not providing a patience diff. If we have --patience, we can
> > say "but we have it, it's just not useful, check for yourself".
>
> Whatever happens, the current deterministic diff algorithm needs to stay
> for generating patch-id's... those really can't be allowed to change.
Oh, there is no discussion about replacing the diff algorithm we have
right now.
Even if we never output patch-ids anywhere, so we always recalculate them,
and therefore would be free to replace the diff algorithm with something
else.
The thing why I do not want patience diff to replace the existing code
is:
- patience diff is slower,
- patience diff is often not worth it (produces the same, maybe even
worse output), and
- patience diff needs the existing code as a fallback anyway.
Where it could possibly help to change existing behavior is with merging.
So maybe somebody has some time to play with, and can apply this patch:
-- snip --
diff --git a/ll-merge.c b/ll-merge.c
index fa2ca52..f731026 100644
--- a/ll-merge.c
+++ b/ll-merge.c
@@ -79,6 +79,8 @@ static int ll_xdl_merge(const struct ll_merge_driver *drv_unused,
memset(&xpp, 0, sizeof(xpp));
if (git_xmerge_style >= 0)
style = git_xmerge_style;
+ if (getenv("GIT_PATIENCE_MERGE"))
+ xpp.flags |= XDF_PATIENCE_DIFF;
return xdl_merge(orig,
src1, name1,
src2, name2,
-- snap --
After compiling and installing, something like this should be fun to
watch:
$ git rev-list --all --parents | \
grep " .* " | \
while read commit parent1 parent2 otherparents
do
test -z "$otherparents" || continue
git checkout $parent1 &&
git merge $parent2 &&
git diff > without-patience.txt &&
git reset --hard $parent1 &&
GIT_PATIENCE_MERGE=1 git merge $parent2 &&
git diff > with-patience.txt &&
if ! cmp without-patience.txt with-patience.txt
then
echo '==============================='
echo "differences found in merge $commit"
echo "without patience: $(wc -l < without-patience.txt)"
echo "with patience: $(wc -l < with-patience.txt)"
echo '-------------------------------'
echo 'without patience:'
cat without-patience.txt
echo '-------------------------------'
echo 'with patience:'
cat with-patience.txt
fi ||
exit
done | tee patience-merge.out
Ciao,
Dscho
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