Merge branch 'jn/plug-empty-tree-leak'

* jn/plug-empty-tree-leak:
merge-recursive: take advantage of hardcoded empty tree
revert: plug memory leak in "cherry-pick root commit" codepath

diff --cc builtin/revert.c
Simple merge

diff --cc merge-recursive.c
Simple merge

diff --cc t/t3503-cherry-pick-root.sh
index 9aefe3a1becac200f2c29beee84fab278f9fcfa0,472e5b80d7ac9b5c90810bd0869510e1e2970f81..e27f39d1e5b0fb0ac3a1fc6417f0f3240934f07d
--- 1/t/t3503-cherry-pick-root.sh
--- 2/t/t3503-cherry-pick-root.sh
+++ b/t/t3503-cherry-pick-root.sh
@@@ -22,31 -29,9 +29,32 @@@ test_expect_success setup 
  
  test_expect_success 'cherry-pick a root commit' '
  
+       git checkout second^0 &&
        git cherry-pick master &&
 -      test first = $(cat file1)
 +      echo first >expect &&
 +      test_cmp expect file1
 +
 +'
 +
 +test_expect_success 'revert a root commit' '
 +
 +      git revert master &&
 +      test_path_is_missing file1
 +
 +'
 +
 +test_expect_success 'cherry-pick a root commit with an external strategy' '
 +
 +      git cherry-pick --strategy=resolve master &&
 +      echo first >expect &&
 +      test_cmp expect file1
 +
 +'
 +
 +test_expect_success 'revert a root commit with an external strategy' '
 +
 +      git revert --strategy=resolve master &&
 +      test_path_is_missing file1
  
  '