Merge branch 'js/maint-am-skip-performance-regression' into maint

* js/maint-am-skip-performance-regression:
  am --skip/--abort: merge HEAD/ORIG_HEAD tree into index

Author: gitster

git-am.sh

@@ -510,7 +510,7 @@ 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"