From: Elijah Newren <newren@xxxxxxxxx>
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@xxxxxxxxxxxx>
Signed-off-by: Elijah Newren <newren@xxxxxxxxx>
---
merge-ort: avoid assuming all renames detected
Fixes https://lore.kernel.org/git/YeHTIfEutLYM4TIU@nand.local/
Changes since v1:
* Fixed a small style issue
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1194%2Fnewren%2Favoid-assertion-assuming-renames-found-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1194/newren/avoid-assertion-assuming-renames-found-v2
Pull-Request: https://github.com/git/git/pull/1194
Range-diff vs v1:
1: f1e9901ae67 ! 1: 239d3ba08c1 merge-ort: avoid assuming all renames detected
@@ merge-ort.c: 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 != 0) {
++ if (renames->needed_limit) {
+ renames->cached_pairs_valid_side = 0;
+ renames->redo_after_renames = 0;
+ }
merge-ort.c | 4 ++
t/t6429-merge-sequence-rename-caching.sh | 67 ++++++++++++++++++++++++
2 files changed, 71 insertions(+)
diff --git a/merge-ort.c b/merge-ort.c
index c3197970219..b0ff9a72879 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -3060,6 +3060,10 @@ 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;
diff --git a/t/t6429-merge-sequence-rename-caching.sh b/t/t6429-merge-sequence-rename-caching.sh
index 035edc40b1e..f2bc8a7d2a2 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
base-commit: 1ffcbaa1a5f10c9f706314d77f88de20a4a498c2
--
gitgitgadget
