revert.c: defer writing CHERRY_PICK_HEAD till it is safe to do so

do_pick_commit() writes out CHERRY_PICK_HEAD before invoking merge (either
via do_recursive_merge() or try_merge_command()) on the assumption that if
the merge fails it is due to conflict. However, if the tree is dirty, the
merge may not even start, aborting before do_pick_commit() can remove
CHERRY_PICK_HEAD.

Instead, defer writing CHERRY_PICK_HEAD till after merge has returned.
At this point we know the merge has either succeeded or failed due
to conflict. In either case, we want CHERRY_PICK_HEAD to be written
so that it may be picked up by the subsequent invocation of commit.

Note that do_recursive_merge() aborts if the merge cannot start, while
try_merge_command() returns a non-zero value other than 1.

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/t/t3507-cherry-pick-conflict.sh b/t/t3507-cherry-pick-conflict.sh
index 212ec54aaf..cb45574a7b 100755
--- a/t/t3507-cherry-pick-conflict.sh
+++ b/t/t3507-cherry-pick-conflict.sh
@@ -77,6 +77,21 @@ test_expect_success 'cherry-pick --no-commit does not set CHERRY_PICK_HEAD' '
 	test_must_fail git rev-parse --verify CHERRY_PICK_HEAD
 '
 
+test_expect_success 'cherry-pick w/dirty tree does not set CHERRY_PICK_HEAD' '
+	pristine_detach initial &&
+	echo foo > foo &&
+	test_must_fail git cherry-pick base &&
+	test_must_fail git rev-parse --verify CHERRY_PICK_HEAD
+'
+
+test_expect_success \
+	'cherry-pick --strategy=resolve w/dirty tree does not set CHERRY_PICK_HEAD' '
+	pristine_detach initial &&
+	echo foo > foo &&
+	test_must_fail git cherry-pick --strategy=resolve base &&
+	test_must_fail git rev-parse --verify CHERRY_PICK_HEAD
+'
+
 test_expect_success 'GIT_CHERRY_PICK_HELP suppresses CHERRY_PICK_HEAD' '
 	pristine_detach initial &&
 	(