From f94bfa151623d7e675db9465ae7ff0b33e4825f3 Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Thu, 12 Dec 2024 10:29:12 +0000 Subject: log: --remerge-diff needs to keep around commit parents To show a remerge diff, the merge needs to be recreated. For that to work, the merge base(s) need to be found, which means that the commits' parents have to be traversed until common ancestors are found (if any). However, one optimization that hails all the way back to cb115748ec0d (Some more memory leak avoidance, 2006-06-17) is to release the commit's list of parents immediately after showing it _and to set that parent list to `NULL`_. This can break the merge base computation. This problem is most obvious when traversing the commits in reverse: In that instance, if a parent of a merge commit has been shown as part of the `git log` command, by the time the merge commit's diff needs to be computed, that parent commit's list of parent commits will have been set to `NULL` and as a result no merge base will be found (even if one should be found). Traversing commits in reverse is far from the only circumstance in which this problem occurs, though. There are many avenues to traversing at least one commit in the revision walk that will later be part of a merge base computation, for example when not even walking any revisions in `git show ` where `` is part of the commit graph between the parents of ``. Another way to force a scenario where a commit is traversed before it has to be traversed again as part of a merge base computation is to start with two revisions (where the first one is reachable from the second but not in a first-parent ancestry) and show the commit log with `--topo-order` and `--first-parent`. Let's fix this by special-casing the `remerge_diff` mode, similar to what we did with reflogs in f35650dff6a4 (log: do not free parents when walking reflog, 2017-07-07). Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- t/t4069-remerge-diff.sh | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 't/t4069-remerge-diff.sh') diff --git a/t/t4069-remerge-diff.sh b/t/t4069-remerge-diff.sh index 07323ebafe..a68c6bfa03 100755 --- a/t/t4069-remerge-diff.sh +++ b/t/t4069-remerge-diff.sh @@ -317,4 +317,11 @@ test_expect_success 'remerge-diff turns off history simplification' ' test_cmp expect actual ' +test_expect_success 'remerge-diff with --reverse' ' + git log -1 --remerge-diff --oneline ab_resolution^ >expect && + git log -1 --remerge-diff --oneline ab_resolution >>expect && + git log -2 --remerge-diff --oneline ab_resolution --reverse >actual && + test_cmp expect actual +' + test_done -- cgit v1.2.3