Re: [PATCH] am --skip/--abort: merge HEAD/ORIG_HEAD tree into index

Johannes Schindelin [off-list ref] writes:

On 2015-09-09 11:10, Johannes Schindelin wrote:

quoted

This is a backport of the corresponding patch to the builtin am in 2.6:
3ecc704 (am --skip/--abort: merge HEAD/ORIG_HEAD tree into index,
2015-08-19).

Reportedly, it can make a huge difference on Windows, in one case a `git
rebase --skip` took 1m40s without, and 5s with, this patch.

Reported-and-suggested-by: Kim Gybels [off-list ref]
Original report: https://github.com/git-for-windows/git/issues/365
Acked-by: Paul Tan <redacted>
Signed-off-by: Johannes Schindelin <redacted>
---
 contrib/examples/git-am.sh | 2 +-

Of course this should be `git-am.sh` in the 2.5.x branch... Could you
adjust that on your side?

"git am -3" is smart enough that applying this patch on a branch
that contains the performance regression does the right thing
without me having to think.  The most time-consuming part on my part
was to figure out which exact commit this change is fixing and then
find out to which maintenance tracks contains that breakage.

Here is what I'll queue on top of maint-2.4 series.

Thanks.

-- >8 --
From: Johannes Schindelin <redacted>
Date: Wed, 9 Sep 2015 09:10:07 +0000
Subject: [PATCH] am --skip/--abort: merge HEAD/ORIG_HEAD tree into index

f8da6801 (am --skip: support skipping while on unborn branch,
2015-06-06) introduced a performance regression to "git am --skip",
where it used "read-tree" to reconstruct the index from scratch
without reusing the cached stat information.

This is a backport of the corresponding patch to the builtin am in 2.6:
3ecc704 (am --skip/--abort: merge HEAD/ORIG_HEAD tree into index,
2015-08-19).

Reportedly, it can make a huge difference on Windows, in one case a `git
rebase --skip` took 1m40s without, and 5s with, this patch.

cf. https://github.com/git-for-windows/git/issues/365

Reported-and-suggested-by: Kim Gybels [off-list ref]
Acked-by: Paul Tan <redacted>
Signed-off-by: Johannes Schindelin <redacted>
Signed-off-by: Junio C Hamano <redacted>
---
 git-am.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/git-am.sh b/git-am.sh
index 3103c0f..4ab1f21 100755
--- a/git-am.sh
+++ b/git-am.sh

@@ -509,7 +509,7 @@ then
 		git read-tree --reset -u $head_tree $head_tree &&
 		index_tree=$(git write-tree) &&
 		git read-tree -m -u $index_tree $head_tree
-		git read-tree $head_tree
+		git read-tree -m $head_tree
 		;;
 	,t)
 		if test -f "$dotest/rebasing"

-- 
2.6.0-rc1-125-gb648220