@matheusbsbs / matheus-bagliano / commits / 9ae39fef7f

merge-ort: avoid assuming all renames detected

In commit 8b09a900a1 ("merge-ort: restart merge with cached renames to reduce process entry cost", 2021-07-16), we noted that in the merge-ort steps of collect_merge_info() detect_and_process_renames() process_entries() that process_entries() was expensive, and we could often make it cheaper by changing this to collect_merge_info() detect_and_process_renames() <cache all the renames, and restart> collect_merge_info() detect_and_process_renames() process_entries() because the second collect_merge_info() would be cheaper (we could avoid traversing into some directories), the second detect_and_process_renames() would be free since we had already detected all renames, and then process_entries() has far fewer entries to handle. However, this was built on the assumption that the first detect_and_process_renames() actually detected all potential renames. If someone has merge.renameLimit set to some small value, that assumption is violated which manifests later with the following message: $ git -c merge.renameLimit=1 rebase upstream ... git: merge-ort.c:546: clear_or_reinit_internal_opts: Assertion `renames->cached_pairs_valid_side == 0' failed. Turn off this cache-renames-and-restart whenever we cannot detect all renames, and add a testcase that would have caught this problem. Reported-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Elijah Newren <newren@gmail.com> Tested-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Elijah Newren committed Jan 17, 2022 at 18:25 UTC 9ae39fef7f3764537e029b57687f6a0a3163e810
2 files changed +71
merge-ort.c
+4
index b346e23ff2..7b2c0e9ee2 100644 --- a/merge-ort.c +++ b/merge-ort.c @@ -3031,6 +3031,10 @@ static int detect_and_process_renames(struct merge_options *opt, trace2_region_enter("merge", "regular renames", opt->repo); detection_run |= detect_regular_renames(opt, MERGE_SIDE1); detection_run |= detect_regular_renames(opt, MERGE_SIDE2); + if (renames->needed_limit) { + renames->cached_pairs_valid_side = 0; + renames->redo_after_renames = 0; + } if (renames->redo_after_renames && detection_run) { int i, side; struct diff_filepair *p;
t/t6429-merge-sequence-rename-caching.sh
+67
index 035edc40b1..f2bc8a7d2a 100755 --- a/t/t6429-merge-sequence-rename-caching.sh +++ b/t/t6429-merge-sequence-rename-caching.sh @@ -697,4 +697,71 @@ test_expect_success 'caching renames only on upstream side, part 2' ' ) ' +# +# The following testcase just creates two simple renames (slightly modified +# on both sides but without conflicting changes), and a directory full of +# files that are otherwise uninteresting. The setup is as follows: +# +# base: unrelated/<BUNCH OF FILES> +# numbers +# values +# upstream: modify: numbers +# modify: values +# topic: add: unrelated/foo +# modify: numbers +# modify: values +# rename: numbers -> sequence +# rename: values -> progression +# +# This is a trivial rename case, but we're curious what happens with a very +# low renameLimit interacting with the restart optimization trying to notice +# that unrelated/ looks like a trivial merge candidate. +# +test_expect_success 'avoid assuming we detected renames' ' + git init redo-weirdness && + ( + cd redo-weirdness && + + mkdir unrelated && + for i in $(test_seq 1 10) + do + >unrelated/$i + done && + test_seq 2 10 >numbers && + test_seq 12 20 >values && + git add numbers values unrelated/ && + git commit -m orig && + + git branch upstream && + git branch topic && + + git switch upstream && + test_seq 1 10 >numbers && + test_seq 11 20 >values && + git add numbers && + git commit -m "Some tweaks" && + + git switch topic && + + >unrelated/foo && + test_seq 2 12 >numbers && + test_seq 12 22 >values && + git add numbers values unrelated/ && + git mv numbers sequence && + git mv values progression && + git commit -m A && + + # + # Actual testing + # + + git switch --detach topic^0 && + + test_must_fail git -c merge.renameLimit=1 rebase upstream && + + git ls-files -u >actual && + ! test_file_is_empty actual + ) +' + test_done