Re: reproducible unexpected behavior for 'git reset'

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

>> I am able to reproduce a scenario where, after a 'commit' and a 'stash
>> pop' that results in a merge conflict, I need to 'reset' a file twice in
>> order to get the index back to HEAD.
>
> Thanks, you found a bug in "git reset [<commit>] -- path" codepath, it
> seems, when dealing with an unmerged path.

This patch is probably a wrong way to fix this issue; I have this
suspicion that the original code for "reset [<commit>] -- paths..."
codepath is correctly designed to deal with unmerged index, and it would
probably need a deeper surgery.

-- >8 --
Subject: [PATCH] reset [<commit>] paths...: do not mishandle unmerged paths

By reading the index with unmerged content before running diff-index
with the tree-ish we are reading from, read_from_tree() function ended
up stuffing the object name from a wrong stage to the resulting index.

Noticed by John Nowak.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

 builtin/reset.c  |    2 +-
 t/t7102-reset.sh |   15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/builtin/reset.c b/builtin/reset.c
index 98bca04..09c8d2a 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -202,7 +202,7 @@ static int read_from_tree(const char *prefix, const char **argv,
 
 	index_fd = hold_locked_index(lock, 1);
 	index_was_discarded = 0;
-	read_cache();
+	read_cache_unmerged();
 	if (do_diff_cache(tree_sha1, &opt))
 		return 1;
 	diffcore_std(&opt);
diff --git a/t/t7102-reset.sh b/t/t7102-reset.sh
index f1cfc9a..1784412 100755
--- a/t/t7102-reset.sh
+++ b/t/t7102-reset.sh
@@ -429,6 +429,21 @@ test_expect_success '--mixed refreshes the index' '
 	test_i18ncmp expect output
 '
 
+test_expect_success 'resetting specific path that is unmerged' '
+	F1=$(git rev-parse HEAD:file1) &&
+	F2=$(git rev-parse HEAD:file2) &&
+	F3=$(git rev-parse HEAD:secondfile) &&
+	{
+		echo "000000 $_z40 0	file2" &&
+		echo "100644 $F1 1	file2" &&
+		echo "100644 $F2 2	file2" &&
+		echo "100644 $F3 3	file2"
+	} | git update-index --index-info &&
+	git ls-files -u &&
+	test_must_fail git reset HEAD file2 &&
+	git diff-index --exit-code --cached HEAD
+'
+
 test_expect_success 'disambiguation (1)' '
 
 	git reset --hard &&