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merge-ort: avoid assuming all renames detected

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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>
This commit is contained in:
Elijah Newren 2022-01-17 18:25:55 +00:00 committed by Junio C Hamano
parent 5fbd2fc599
commit 9ae39fef7f
2 changed files with 71 additions and 0 deletions
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4
merge-ort.c
View File

@ -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;

67
t/t6429-merge-sequence-rename-caching.sh
View File

@ -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