Have a repo with a subtree merge, do a 'git log --follow prefix/test.c', the output only contains history in the outer repo, not commits that were merged via a subtree merge.
This is inconsistent, since doing a 'git blame prefix/test.c' does find the original commits. This works because find_rename() in blame.c is invoked for each parent, and there diff_tree_oid() is used, which uses try_to_follow_renames(). This means that in case a rename happens as part of a merge commit, git blame can follow that rename.
Fix the problem in a similar way for the 'git log --follow' case: in case log_tree_diff() finds a merge commit and it would return early, then do some extra work in the follow_renames case first. Check each parent, use diff_tree_oid() and if found_follow is set, then work with that parent instead of returning.
This means that users examining the history of a repo with subtree merges can see all commits to a file with a single 'git log --follow' invocation, instead of one invocation for the outer repo and one for the history before the subtree merge.
Signed-off-by: Miklos Vajna <vmiklos@collabora.com> ---
Hi,
I recently ran into a case where a subtree merge was used to do a one-off import of one repo into an other one, into a subdirectory. Turns out git blame finds original commits nicely, but git log --follow is less great for this case. This is an improvement to also follow renames when the rename happens as part of a merge commit.
Let me know if I managed to get some formality wrong, I haven't contributed since 2022.
Could you please review this?
Thanks,
Miklos
log-tree.c | 20 ++++++++++++++++- t/meson.build | 1 + t/t4218-log-follow-subtree-merge.sh | 34 +++++++++++++++++++++++++++++ 3 files changed, 54 insertions(+), 1 deletion(-) create mode 100755 t/t4218-log-follow-subtree-merge.sh
Show changes to 3 files +54 −1
log-tree.c, t/meson.build, t/t4218-log-follow-subtree-merge.sh
diff --git a/log-tree.c b/log-tree.c index 7e048701d0..bce09c7dac 100644 --- a/log-tree.c +++ b/log-tree.c @@ -1142,8 +1142,26 @@ static int log_tree_diff(struct rev_info *opt, struct commit *commit, struct log /* Show parent info for multiple diffs */ log->parent = parents->item; } - } else + } else { + if (opt->diffopt.flags.follow_renames) { + /* + * Detect a rename across one of the parents. + * Check each parent till we find a follow. + */ + struct commit_list *p; + for (p = parents; p; p = p->next) { + parse_commit_or_die(p->item); + diff_tree_oid(get_commit_tree_oid(p->item), + oid, "", &opt->diffopt); + diff_queue_clear(&diff_queued_diff); + if (opt->diffopt.found_follow) { + opt->diffopt.found_follow = 0; + break; + } + } + } return 0; + } } showed_log = 0; diff --git a/t/meson.build b/t/meson.build index 7528e5cda5..b4ae8d76d8 100644 --- a/t/meson.build +++ b/t/meson.build @@ -574,6 +574,7 @@ integration_tests = [ 't4215-log-skewed-merges.sh', 't4216-log-bloom.sh', 't4217-log-limit.sh', + 't4218-log-follow-subtree-merge.sh', 't4252-am-options.sh', 't4253-am-keep-cr-dos.sh', 't4254-am-corrupt.sh', diff --git a/t/t4218-log-follow-subtree-merge.sh b/t/t4218-log-follow-subtree-merge.sh new file mode 100755 index 0000000000..7ca607cbb8 --- /dev/null +++ b/t/t4218-log-follow-subtree-merge.sh @@ -0,0 +1,34 @@ +#!/bin/sh + +test_description='Test --follow follows renames across subtree merges' + +GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master +export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME + +. ./test-lib.sh + +test_expect_success 'setup subtree-merged repository' ' + git init inner && + echo inner >inner/inner.txt && + git -C inner add inner.txt && + git -C inner commit -m "inner init" && + + git init outer && + echo outer >outer/outer.txt && + git -C outer add outer.txt && + git -C outer commit -m "outer init" && + + git -C outer fetch ../inner master && + git -C outer merge -s ours --no-commit --allow-unrelated-histories \ + FETCH_HEAD && + git -C outer read-tree --prefix=inner/ -u FETCH_HEAD && + git -C outer commit -m "Merge inner repo into inner/ subdirectory" +' + +test_expect_success '--follow finds the pre-merge commit through a subtree merge' ' + git -C outer log --follow --pretty=tformat:%s inner/inner.txt >actual && + echo "inner init" >expect && + test_cmp expect actual +' + +test_done
-- 2.51.0