Re: [PATCH 3/3] merge-recursive: Avoid incorporating uncommitted changes in a merge
From: Junio C Hamano <hidden>
Date: 2017-12-22 20:38:28
Elijah Newren [off-list ref] writes:
builtin/merge.c contains this important requirement for merge strategies: /* * At this point, we need a real merge. No matter what strategy * we use, it would operate on the index, possibly affecting the * working tree, and when resolved cleanly, have the desired * tree in the index -- this means that the index must be in * sync with the head commit. The strategies are responsible * to ensure this. */ merge-recursive does not do this check directly, instead it relies on unpack_trees() to do it. However, merge_trees() has a special check for the merge branch exactly matching the merge base; when it detects that situation, it returns early without calling unpack_trees(), because it knows that the HEAD commit already has the correct result. Unfortunately, it didn't check that the index matched HEAD, so after it returned, the outer logic ended up creating a merge commit that included something other than HEAD.
Good. I actually was imagining that you would shoot for creating an empty commit and leaving a working tree and the index that are both dirty, but I do not think it is worth the effort. Besides, "you have to start from a clean index" is a much simpler rule to explain than with "unless the resulting tree is the same as HEAD", especially when that "unless" is highly unlikely to happen anyway. Thanks.
quoted hunk
Signed-off-by: Elijah Newren <redacted> --- merge-recursive.c | 7 +++++++ t/t6044-merge-unrelated-index-changes.sh | 2 +- 2 files changed, 8 insertions(+), 1 deletion(-)diff --git a/merge-recursive.c b/merge-recursive.c index 2ecf495cc2..780f81a8bd 100644 --- a/merge-recursive.c +++ b/merge-recursive.c@@ -1952,6 +1952,13 @@ int merge_trees(struct merge_options *o, } if (oid_eq(&common->object.oid, &merge->object.oid)) { + struct strbuf sb = STRBUF_INIT; + + if (index_has_changes(&sb)) { + err(o, _("Dirty index: cannot merge (dirty: %s)"), + sb.buf); + return 0; + } output(o, 0, _("Already up to date!")); *result = head; return 1;diff --git a/t/t6044-merge-unrelated-index-changes.sh b/t/t6044-merge-unrelated-index-changes.sh index 5e472be92b..23b86fb977 100755 --- a/t/t6044-merge-unrelated-index-changes.sh +++ b/t/t6044-merge-unrelated-index-changes.sh@@ -112,7 +112,7 @@ test_expect_success 'recursive' ' test_must_fail git merge -s recursive C^0 ' -test_expect_failure 'recursive, when merge branch matches merge base' ' +test_expect_success 'recursive, when merge branch matches merge base' ' git reset --hard && git checkout B^0 &&