[PATCH] merge-ort: avoid assuming all renames detected

[PATCH] merge-ort: avoid assuming all renames detected

[Elijah Newren via GitGitGadget]

From: Elijah Newren <newren@gmail.com>

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>
---
    merge-ort: avoid assuming all renames detected
    
    Fixes https://lore.kernel.org/git/YeHTIfEutLYM4TIU@nand.local/

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1194%2Fnewren%2Favoid-assertion-assuming-renames-found-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1194/newren/avoid-assertion-assuming-renames-found-v1
Pull-Request: https://github.com/git/git/pull/1194

 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..143d274f117 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 != 0) {
+		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

Re: [PATCH] merge-ort: avoid assuming all renames detected

[Junio C Hamano]

"Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Elijah Newren <newren@gmail.com>
>
> 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>
> ---

Thanks.  Will fork from maint-2.33 and park on 'seen' for now.

Re: [PATCH] merge-ort: avoid assuming all renames detected

[Junio C Hamano]

"Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:

> diff --git a/merge-ort.c b/merge-ort.c
> index c3197970219..143d274f117 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 != 0) {

Don't compare with NULL or 0, i.e.

	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;

[PATCH v2] merge-ort: avoid assuming all renames detected

[Elijah Newren via GitGitGadget]

From: Elijah Newren <newren@gmail.com>

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>
---
    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

Re: [PATCH v2] merge-ort: avoid assuming all renames detected

[Junio C Hamano]

"Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Elijah Newren <newren@gmail.com>
>
> 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>
> ---

Thanks.  An Ack?

>     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

Re: [PATCH v2] merge-ort: avoid assuming all renames detected

[Elijah Newren]

On Mon, Jan 17, 2022 at 11:33 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> "Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > From: Elijah Newren <newren@gmail.com>
> >
> > 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>
> > ---
>
> Thanks.  An Ack?

Taylor told me the code change fixed his case, and that he'd review my
full patch with the testcase when I posted it.  Let's wait to hear
from him.

Re: [PATCH v2] merge-ort: avoid assuming all renames detected

[Taylor Blau]

On Mon, Jan 17, 2022 at 01:21:11PM -0800, Elijah Newren wrote:
> On Mon, Jan 17, 2022 at 11:33 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> > Thanks.  An Ack?
>
> Taylor told me the code change fixed his case, and that he'd review my
> full patch with the testcase when I posted it.  Let's wait to hear
> from him.

Ack. I can't vouch for the ort-specific details, but I trust Elijah's
judgement (obviously). Running a version of Git with this patch applied
fixes the issue I originally reported.

Thanks, Elijah!

Re: [PATCH v2] merge-ort: avoid assuming all renames detected

[Junio C Hamano]

Taylor Blau <me@ttaylorr.com> writes:

> On Mon, Jan 17, 2022 at 01:21:11PM -0800, Elijah Newren wrote:
>> On Mon, Jan 17, 2022 at 11:33 AM Junio C Hamano <gitster@pobox.com> wrote:
>>
>> > Thanks.  An Ack?
>>
>> Taylor told me the code change fixed his case, and that he'd review my
>> full patch with the testcase when I posted it.  Let's wait to hear
>> from him.
>
> Ack. I can't vouch for the ort-specific details, but I trust Elijah's
> judgement (obviously). Running a version of Git with this patch applied
> fixes the issue I originally reported.
>
> Thanks, Elijah!

Thanks.  Will queue with your Tested-by, then.

Thank you very much, both of you.

Re: [PATCH v2] merge-ort: avoid assuming all renames detected

[Junio C Hamano]

Elijah Newren <newren@gmail.com> writes:

> On Mon, Jan 17, 2022 at 11:33 AM Junio C Hamano <gitster@pobox.com> wrote:
>>
>> "Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:
>>
>> > From: Elijah Newren <newren@gmail.com>
>> >
>> > 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>
>> > ---
>>
>> Thanks.  An Ack?
>
> Taylor told me the code change fixed his case, and that he'd review my
> full patch with the testcase when I posted it.  Let's wait to hear
> from him.

Yes, I am waiting (notice who is on To: and not Cc: on the message
you are responding to ;-).

Thanks.

Re: [PATCH v2] merge-ort: avoid assuming all renames detected

[SZEDER Gábor]

On Mon, Jan 17, 2022 at 06:25:55PM +0000, Elijah Newren via GitGitGadget wrote:
> 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

There is no 'test_file_is_empty' function, but because of the ! at the
beginning of the line it didn't fail the test.

The minimal fix would be to use 'test_file_not_empty' instead, but I
wonder whether we should use 'test_line_count = 2' instead for a tad
tighter check.

> +	)
> +'
> +
>  test_done
> 
> base-commit: 1ffcbaa1a5f10c9f706314d77f88de20a4a498c2
> -- 
> gitgitgadget

Re: [PATCH v2] merge-ort: avoid assuming all renames detected

[Elijah Newren]

On Thu, Jun 30, 2022 at 2:54 AM SZEDER Gábor <szeder.dev@gmail.com> wrote:
>
> On Mon, Jan 17, 2022 at 06:25:55PM +0000, Elijah Newren via GitGitGadget wrote:
> > 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
>
> There is no 'test_file_is_empty' function, but because of the ! at the
> beginning of the line it didn't fail the test.

Oops, looks like I meant test_must_be_empty.

> The minimal fix would be to use 'test_file_not_empty' instead, but I
> wonder whether we should use 'test_line_count = 2' instead for a tad
> tighter check.

Makes sense; since this merged about half a year ago, I'll submit a
new patch to fix this.  Thanks for catching and pointing it out!



>
> > +     )
> > +'
> > +
> >  test_done
> >
> > base-commit: 1ffcbaa1a5f10c9f706314d77f88de20a4a498c2
> > --
> > gitgitgadget

Re: [PATCH v2] merge-ort: avoid assuming all renames detected

[Elijah Newren]

On Thu, Jun 30, 2022 at 7:30 PM Elijah Newren <newren@gmail.com> wrote:
>
> On Thu, Jun 30, 2022 at 2:54 AM SZEDER Gábor <szeder.dev@gmail.com> wrote:
> >
> > On Mon, Jan 17, 2022 at 06:25:55PM +0000, Elijah Newren via GitGitGadget wrote:
> > > 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
[...]
> > > +             git ls-files -u >actual &&
> > > +             ! test_file_is_empty actual
> >
> > There is no 'test_file_is_empty' function, but because of the ! at the
> > beginning of the line it didn't fail the test.
>
> Oops, looks like I meant test_must_be_empty.
>
> > The minimal fix would be to use 'test_file_not_empty' instead, but I
> > wonder whether we should use 'test_line_count = 2' instead for a tad
> > tighter check.
>
> Makes sense; since this merged about half a year ago, I'll submit a
> new patch to fix this.  Thanks for catching and pointing it out!

Submitted over here:
https://lore.kernel.org/git/pull.1276.git.1656652799863.gitgitgadget@gmail.com/