[PATCH] Fixed --shallow-since generating descendant borders

[PATCH] Fixed --shallow-since generating descendant borders

[Samo Pogačnik via GitGitGadget]

From: =?UTF-8?q?Samo=20Poga=C4=8Dnik?= <samo_pogacnik@t-2.net>

When shallow cloning based on a date, it happens that a list
of commits is received, where some of the list border commits
actually descend one from another. In such cases borders need
to be expanded by additional parents and excluding the child
as border.

Signed-off-by: Samo Pogačnik <samo_pogacnik@t-2.net>
---
    Fixed --shallow-since generating descendant borders
    
    When shallow cloning based on a date, it happens that a list of commits
    is received, where some of the list border commits actually descend one
    from another. In such cases borders need to be expanded by additional
    parents and excluding the child as border.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2107%2Fspog%2Ffix-shallow-since-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2107/spog/fix-shallow-since-v1
Pull-Request: https://github.com/git/git/pull/2107

 shallow.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/shallow.c b/shallow.c
index 55b9cd9d3f..37079a0bf1 100644
--- a/shallow.c
+++ b/shallow.c
@@ -251,21 +251,50 @@ struct commit_list *get_shallow_commits_by_rev_list(struct strvec *argv,
 	 * commit A is processed first, then commit B, whose parent is
 	 * A, later. If NOT_SHALLOW on A is cleared at step 1, B
 	 * itself is considered border at step 2, which is incorrect.
+	 * We must also consider that B has multiple parents, some of
+	 * them not being in the not_shallow_list, but must be added
+	 * as border commits to the result.
+	 *
+	 * The general processing goes like this:
+	 * 1. Above we've coloured the whole not_shallow_list of commits
+	 *    with 'not_shallow'.
+	 * 2. For each commit from the not_shallow_list (the code below)
+	 *    we colour 'shallow' the commit and its parents, which are not
+	 *    already coloured 'not_shallow'.
+	 * 3. Commits with all parents being coloured only 'shallow' remain
+	 *    shallow and are being added to result list.
+	 * 4. Commits without all parents being coloured only 'shallow' are
+	 *    being excluded as borders, however their parents coloured only
+	 *    'shallow' are being added to the result borders list.
 	 */
 	for (p = not_shallow_list; p; p = p->next) {
 		struct commit *c = p->item;
 		struct commit_list *parent;
+		int must_not_be_shallow = 0;
 
 		if (repo_parse_commit(the_repository, c))
 			die("unable to parse commit %s",
 			    oid_to_hex(&c->object.oid));
 
 		for (parent = c->parents; parent; parent = parent->next)
-			if (!(parent->item->object.flags & not_shallow_flag)) {
+			if (parent->item->object.flags & not_shallow_flag) {
+				must_not_be_shallow = 1;
+			} else {
 				c->object.flags |= shallow_flag;
-				commit_list_insert(c, &result);
-				break;
+				parent->item->object.flags |= shallow_flag;
 			}
+		if (must_not_be_shallow) {
+			c->object.flags &= ~shallow_flag;
+			for (parent = c->parents; parent; parent = parent->next)
+				if (parent->item->object.flags & shallow_flag) {
+					parent->item->object.flags |= not_shallow_flag;
+					commit_list_insert(parent->item, &result);
+				}
+		} else {
+			for (parent = c->parents; parent; parent = parent->next)
+				parent->item->object.flags &= ~shallow_flag;
+			commit_list_insert(c, &result);
+		}
 	}
 	free_commit_list(not_shallow_list);
 

base-commit: debbc87557487aa9a8ed8a35367d17f8b4081c76
-- 
gitgitgadget

Re: [PATCH] Fixed --shallow-since generating descendant borders

[Junio C Hamano]

"Samo Pogačnik via GitGitGadget" <gitgitgadget@gmail.com> writes:

> Subject: Re: [PATCH] Fixed --shallow-since generating descendant borders

A patch title wants maximum information density, and "Fixed" is a
vague verb in that context, as it does not tell what existing
behaviour was wrong or what is the right alternative behaviour.

As "git log --oneline --no-merges" can show, our patches typically
begins with the area the change pertains to plus a colon.  "git log
--oneline shallow.c" (which is the file this patch touches) shows a
handful ones that are prefixed with "shallow:".

What to write after the "<area>:" prefix for this patch, I am not
sure, as the body of the proposed log message does not discuss the
bad effect of the suboptimal or wrong (I cannot even tell which one
from the proposed log message) behaviour.

> From: =?UTF-8?q?Samo=20Poga=C4=8Dnik?= <samo_pogacnik@t-2.net>
>
> When shallow cloning based on a date, it happens that a list
> of commits is received, where some of the list border commits
> actually descend one from another. In such cases borders need
> to be expanded by additional parents and excluding the child
> as border.

Missing from the above description are

 - received by whom?

 - the reason why they want such a list is to do what?

 - when there are multiple borders that can be "expanded", and if
   you leave it unexpanded (i.e., the behaviour of the current code)
   what happens and why is it bad?  Is it breaking bad (e.g., clone
   would be aborted, the resulting cloned repository does not pass
   fsck), or is it suboptimal bad (e.g., we told the command that we
   do not want commits older than date X, but we end up having more
   commits)?

 - what is the cost of computing the "expansion", relative to the
   above "badness"?  Fixing a breaking bad behaviour can of course
   afford to spend more cycles than a suboptimal bad behaviour.

The usual way to compose a log message of this project is to

 - Give an observation on how the current system works in the
   present tense (so no need to say "Currently X is Y", or
   "Previously X was Y" to describe the state before your change;
   just "X is Y" is enough), and discuss what you perceive as a
   problem in it.

 - Propose a solution (optional---often, problem description
   trivially leads to an obvious solution in reader's minds).

 - Give commands to somebody editing the codebase to "make it so",
   instead of saying "This commit does X".

in this order.

> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2107%2Fspog%2Ffix-shallow-since-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2107/spog/fix-shallow-since-v1
> Pull-Request: https://github.com/git/git/pull/2107
>
>  shallow.c | 35 ++++++++++++++++++++++++++++++++---
>  1 file changed, 32 insertions(+), 3 deletions(-)

We'd want to protect this change from other people accidentally
breaking it in the future, and the best practice we have is to write
a test to observe end-user visible behaviour.  The whole helper
function being touched by the patch came in the 27-patch series
merged at a460ea4a (Merge branch 'nd/shallow-deepen', 2016-10-10),
and it seems to have added to t5500-fetch-pack.sh to cover the
"--shallow-since" feature.  Perhaps this should add a few tests to
demonstrate existing "breakage" (i.e., a "test_expect_success" test
that would fail without the change in the patch to shallow.c we see
below, and would succeed when the patch to shallow.c is applied).

Thanks.

[PATCH v2] shallow: set borders which are all reachable after clone shallow since

[Samo Pogačnik via GitGitGadget]

From: =?UTF-8?q?Samo=20Poga=C4=8Dnik?= <samo_pogacnik@t-2.net>

When shallow cloning based on a date, it happens that not all
shallow border commits are reachable.

Original implementation of a generic shallow boundary finder
based on rev-list sets a commit (from the initial list of border
commit candidates) to be the border commit as soon as it finds one
of its parentis that wasn't on the list of initial candidates. This
results in a successful shallow clone, where some of its declared
border commits may not be reachable and they would not actually exist
in the cloned repository. Thus the result may contradict existing
comment in the code, which correctly states that such commmit should
not be considered border.

One can inspect such case by running the added test scenario:
- 'clone shallow since all borders reachable'

The modified implementation of a generic shallow boundary finder
based on rev-list ensures that all shallow border commits are reachable
also after being grafted. This is achieved by inspecting all parents
of each initial border commit candidate. The border commit candidate
is set border only when all its parents wern't on the initial list of
candidates. Otherwise the border commit candidate is not set as border
however its parents that weren't on the list of candidates are set as
borders.

Signed-off-by: Samo Pogačnik <samo_pogacnik@t-2.net>
---
    Fixed --shallow-since generating descendant borders
    
    When shallow cloning based on a date, it happens that a list of commits
    is received, where some of the list border commits actually descend one
    from another. In such cases borders need to be expanded by additional
    parents and excluding the child as border.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2107%2Fspog%2Ffix-shallow-since-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2107/spog/fix-shallow-since-v2
Pull-Request: https://github.com/git/git/pull/2107

Range-diff vs v1:

 1:  aaeff44f83 ! 1:  479692c386 Fixed --shallow-since generating descendant borders
     @@ Metadata
      Author: Samo Pogačnik <samo_pogacnik@t-2.net>
      
       ## Commit message ##
     -    Fixed --shallow-since generating descendant borders
     +    shallow: set borders which are all reachable after clone shallow since
      
     -    When shallow cloning based on a date, it happens that a list
     -    of commits is received, where some of the list border commits
     -    actually descend one from another. In such cases borders need
     -    to be expanded by additional parents and excluding the child
     -    as border.
     +    When shallow cloning based on a date, it happens that not all
     +    shallow border commits are reachable.
     +
     +    Original implementation of a generic shallow boundary finder
     +    based on rev-list sets a commit (from the initial list of border
     +    commit candidates) to be the border commit as soon as it finds one
     +    of its parentis that wasn't on the list of initial candidates. This
     +    results in a successful shallow clone, where some of its declared
     +    border commits may not be reachable and they would not actually exist
     +    in the cloned repository. Thus the result may contradict existing
     +    comment in the code, which correctly states that such commmit should
     +    not be considered border.
     +
     +    One can inspect such case by running the added test scenario:
     +    - 'clone shallow since all borders reachable'
     +
     +    The modified implementation of a generic shallow boundary finder
     +    based on rev-list ensures that all shallow border commits are reachable
     +    also after being grafted. This is achieved by inspecting all parents
     +    of each initial border commit candidate. The border commit candidate
     +    is set border only when all its parents wern't on the initial list of
     +    candidates. Otherwise the border commit candidate is not set as border
     +    however its parents that weren't on the list of candidates are set as
     +    borders.
      
          Signed-off-by: Samo Pogačnik <samo_pogacnik@t-2.net>
      
     @@ shallow.c: struct commit_list *get_shallow_commits_by_rev_list(struct strvec *ar
       	 * commit A is processed first, then commit B, whose parent is
       	 * A, later. If NOT_SHALLOW on A is cleared at step 1, B
       	 * itself is considered border at step 2, which is incorrect.
     -+	 * We must also consider that B has multiple parents, some of
     -+	 * them not being in the not_shallow_list, but must be added
     -+	 * as border commits to the result.
     ++	 *
     ++	 * We must also consider that B has multiple parents which may
     ++	 * not all be marked NOT_SHALLOW (as they weren't traversed into
     ++	 * the not_shallow_list from revs in the first place). Because of
     ++	 * that an additional step is required to reconsider B as border.
     ++	 * A commit from the not_shallow_list is considered border only
     ++	 * when ALL its parents weren't on the not_shallow_list.
     ++	 * When one or more parents of a commit from the not_shellow_list
     ++	 * also come from that list, the commit is not considered border,
     ++	 * but its non-listed parents are considered border commits.
      +	 *
      +	 * The general processing goes like this:
     -+	 * 1. Above we've coloured the whole not_shallow_list of commits
     -+	 *    with 'not_shallow'.
     ++	 * 1. Above we've painted the whole not_shallow_list of commits
     ++	 *    NOT_SHALLOW.
      +	 * 2. For each commit from the not_shallow_list (the code below)
     -+	 *    we colour 'shallow' the commit and its parents, which are not
     -+	 *    already coloured 'not_shallow'.
     -+	 * 3. Commits with all parents being coloured only 'shallow' remain
     ++	 *    we paint SHALLOW this commit and its parent for all its
     ++	 *    parents that had not yet been painted NOT_SHALLOW.
     ++	 * 3. Commits with all parents being painted only SHALLOW remain
      +	 *    shallow and are being added to result list.
     -+	 * 4. Commits without all parents being coloured only 'shallow' are
     -+	 *    being excluded as borders, however their parents coloured only
     -+	 *    'shallow' are being added to the result borders list.
     ++	 * 4. Commits without all parents being painted only SHALLOW are
     ++	 *    being excluded as borders, however their parents painted only
     ++	 *    SHALLOW are being added to the result borders list.
       	 */
       	for (p = not_shallow_list; p; p = p->next) {
       		struct commit *c = p->item;
     @@ shallow.c: struct commit_list *get_shallow_commits_by_rev_list(struct strvec *ar
       	}
       	free_commit_list(not_shallow_list);
       
     +
     + ## t/t5500-fetch-pack.sh ##
     +@@ t/t5500-fetch-pack.sh: test_expect_success 'shallow since with commit graph and already-seen commit' '
     + 	)
     + '
     + 
     ++test_expect_success 'clone shallow since all borders reachable' '
     ++	test_create_repo shallow-since-all-borders-reachable &&
     ++	(
     ++	rm -rf shallow123 &&
     ++	cd shallow-since-all-borders-reachable &&
     ++	GIT_COMMITTER_DATE="2025-08-19 12:34:56" git commit --allow-empty -m one &&
     ++	GIT_COMMITTER_DATE="2025-08-20 12:34:56" git switch -c branch &&
     ++	GIT_COMMITTER_DATE="2025-08-21 12:34:56" git commit --allow-empty -m two &&
     ++	GIT_COMMITTER_DATE="2025-08-22 12:34:56" git commit --allow-empty -m three &&
     ++	GIT_COMMITTER_DATE="2025-08-23 12:34:56" git switch main &&
     ++	GIT_COMMITTER_DATE="2025-08-24 12:34:56" git merge branch --no-ff &&
     ++	GIT_COMMITTER_DATE="2025-08-26 12:34:56" git clone --shallow-since "2025-08-21 12:34:56" "file://$(pwd)/." ../shallow123 &&
     ++	cd ../shallow123 &&
     ++	echo "Shallow borders:" &&
     ++	cat .git/shallow &&
     ++	$(for commit in $(cat .git/shallow); do git rev-list $commit 1>/dev/null || exit 1; done)
     ++	)
     ++'
     ++
     + test_expect_success 'shallow clone exclude tag two' '
     + 	test_create_repo shallow-exclude &&
     + 	(


 shallow.c             | 42 +++++++++++++++++++++++++++++++++++++++---
 t/t5500-fetch-pack.sh | 19 +++++++++++++++++++
 2 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/shallow.c b/shallow.c
index 55b9cd9d3f..2929ac90ee 100644
--- a/shallow.c
+++ b/shallow.c
@@ -251,21 +251,57 @@ struct commit_list *get_shallow_commits_by_rev_list(struct strvec *argv,
 	 * commit A is processed first, then commit B, whose parent is
 	 * A, later. If NOT_SHALLOW on A is cleared at step 1, B
 	 * itself is considered border at step 2, which is incorrect.
+	 *
+	 * We must also consider that B has multiple parents which may
+	 * not all be marked NOT_SHALLOW (as they weren't traversed into
+	 * the not_shallow_list from revs in the first place). Because of
+	 * that an additional step is required to reconsider B as border.
+	 * A commit from the not_shallow_list is considered border only
+	 * when ALL its parents weren't on the not_shallow_list.
+	 * When one or more parents of a commit from the not_shellow_list
+	 * also come from that list, the commit is not considered border,
+	 * but its non-listed parents are considered border commits.
+	 *
+	 * The general processing goes like this:
+	 * 1. Above we've painted the whole not_shallow_list of commits
+	 *    NOT_SHALLOW.
+	 * 2. For each commit from the not_shallow_list (the code below)
+	 *    we paint SHALLOW this commit and its parent for all its
+	 *    parents that had not yet been painted NOT_SHALLOW.
+	 * 3. Commits with all parents being painted only SHALLOW remain
+	 *    shallow and are being added to result list.
+	 * 4. Commits without all parents being painted only SHALLOW are
+	 *    being excluded as borders, however their parents painted only
+	 *    SHALLOW are being added to the result borders list.
 	 */
 	for (p = not_shallow_list; p; p = p->next) {
 		struct commit *c = p->item;
 		struct commit_list *parent;
+		int must_not_be_shallow = 0;
 
 		if (repo_parse_commit(the_repository, c))
 			die("unable to parse commit %s",
 			    oid_to_hex(&c->object.oid));
 
 		for (parent = c->parents; parent; parent = parent->next)
-			if (!(parent->item->object.flags & not_shallow_flag)) {
+			if (parent->item->object.flags & not_shallow_flag) {
+				must_not_be_shallow = 1;
+			} else {
 				c->object.flags |= shallow_flag;
-				commit_list_insert(c, &result);
-				break;
+				parent->item->object.flags |= shallow_flag;
 			}
+		if (must_not_be_shallow) {
+			c->object.flags &= ~shallow_flag;
+			for (parent = c->parents; parent; parent = parent->next)
+				if (parent->item->object.flags & shallow_flag) {
+					parent->item->object.flags |= not_shallow_flag;
+					commit_list_insert(parent->item, &result);
+				}
+		} else {
+			for (parent = c->parents; parent; parent = parent->next)
+				parent->item->object.flags &= ~shallow_flag;
+			commit_list_insert(c, &result);
+		}
 	}
 	free_commit_list(not_shallow_list);
 
diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
index 2677cd5faa..12209887fb 100755
--- a/t/t5500-fetch-pack.sh
+++ b/t/t5500-fetch-pack.sh
@@ -904,6 +904,25 @@ test_expect_success 'shallow since with commit graph and already-seen commit' '
 	)
 '
 
+test_expect_success 'clone shallow since all borders reachable' '
+	test_create_repo shallow-since-all-borders-reachable &&
+	(
+	rm -rf shallow123 &&
+	cd shallow-since-all-borders-reachable &&
+	GIT_COMMITTER_DATE="2025-08-19 12:34:56" git commit --allow-empty -m one &&
+	GIT_COMMITTER_DATE="2025-08-20 12:34:56" git switch -c branch &&
+	GIT_COMMITTER_DATE="2025-08-21 12:34:56" git commit --allow-empty -m two &&
+	GIT_COMMITTER_DATE="2025-08-22 12:34:56" git commit --allow-empty -m three &&
+	GIT_COMMITTER_DATE="2025-08-23 12:34:56" git switch main &&
+	GIT_COMMITTER_DATE="2025-08-24 12:34:56" git merge branch --no-ff &&
+	GIT_COMMITTER_DATE="2025-08-26 12:34:56" git clone --shallow-since "2025-08-21 12:34:56" "file://$(pwd)/." ../shallow123 &&
+	cd ../shallow123 &&
+	echo "Shallow borders:" &&
+	cat .git/shallow &&
+	$(for commit in $(cat .git/shallow); do git rev-list $commit 1>/dev/null || exit 1; done)
+	)
+'
+
 test_expect_success 'shallow clone exclude tag two' '
 	test_create_repo shallow-exclude &&
 	(

base-commit: debbc87557487aa9a8ed8a35367d17f8b4081c76
-- 
gitgitgadget

Re: [PATCH v2] shallow: set borders which are all reachable after clone shallow since

[Junio C Hamano]

"Samo Pogačnik via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: =?UTF-8?q?Samo=20Poga=C4=8Dnik?= <samo_pogacnik@t-2.net>
>
> When shallow cloning based on a date, it happens that not all
> shallow border commits are reachable.
>
> Original implementation of a generic shallow boundary finder
> based on rev-list sets a commit (from the initial list of border
> commit candidates) to be the border commit as soon as it finds one
> of its parentis that wasn't on the list of initial candidates. This
> results in a successful shallow clone, where some of its declared
> border commits may not be reachable and they would not actually exist
> in the cloned repository. Thus the result may contradict existing
> comment in the code, which correctly states that such commmit should
> not be considered border.
>
> One can inspect such case by running the added test scenario:
> - 'clone shallow since all borders reachable'
>
> The modified implementation of a generic shallow boundary finder
> based on rev-list ensures that all shallow border commits are reachable
> also after being grafted. This is achieved by inspecting all parents
> of each initial border commit candidate. The border commit candidate
> is set border only when all its parents wern't on the initial list of
> candidates. Otherwise the border commit candidate is not set as border
> however its parents that weren't on the list of candidates are set as
> borders.

It is a minor point, but there are "boundary" and "border" used more
or less interchangeably in the proposed commit log message, and
would make the readers wonder if there are differences (I do not
think we use the word "border" anywhere in our documentation).  It
is minor as we do not have such mixture in the end-user facing part
of the documentation with this patch.

I'll let those (cc'ed) who may be more familiar with, or, at least
have more code than I have in, the shallow infrastructure to comment
on the way the updated code uses the revision machinery.

Thanks.

> diff --git a/shallow.c b/shallow.c
> index 55b9cd9d3f..2929ac90ee 100644
> --- a/shallow.c
> +++ b/shallow.c
> @@ -251,21 +251,57 @@ struct commit_list *get_shallow_commits_by_rev_list(struct strvec *argv,
>  	 * commit A is processed first, then commit B, whose parent is
>  	 * A, later. If NOT_SHALLOW on A is cleared at step 1, B
>  	 * itself is considered border at step 2, which is incorrect.
> +	 *
> +	 * We must also consider that B has multiple parents which may
> +	 * not all be marked NOT_SHALLOW (as they weren't traversed into
> +	 * the not_shallow_list from revs in the first place). Because of
> +	 * that an additional step is required to reconsider B as border.
> +	 * A commit from the not_shallow_list is considered border only
> +	 * when ALL its parents weren't on the not_shallow_list.
> +	 * When one or more parents of a commit from the not_shellow_list
> +	 * also come from that list, the commit is not considered border,
> +	 * but its non-listed parents are considered border commits.
> +	 *
> +	 * The general processing goes like this:
> +	 * 1. Above we've painted the whole not_shallow_list of commits
> +	 *    NOT_SHALLOW.
> +	 * 2. For each commit from the not_shallow_list (the code below)
> +	 *    we paint SHALLOW this commit and its parent for all its
> +	 *    parents that had not yet been painted NOT_SHALLOW.
> +	 * 3. Commits with all parents being painted only SHALLOW remain
> +	 *    shallow and are being added to result list.
> +	 * 4. Commits without all parents being painted only SHALLOW are
> +	 *    being excluded as borders, however their parents painted only
> +	 *    SHALLOW are being added to the result borders list.
>  	 */
>  	for (p = not_shallow_list; p; p = p->next) {
>  		struct commit *c = p->item;
>  		struct commit_list *parent;
> +		int must_not_be_shallow = 0;
>  
>  		if (repo_parse_commit(the_repository, c))
>  			die("unable to parse commit %s",
>  			    oid_to_hex(&c->object.oid));
>  
>  		for (parent = c->parents; parent; parent = parent->next)
> -			if (!(parent->item->object.flags & not_shallow_flag)) {
> +			if (parent->item->object.flags & not_shallow_flag) {
> +				must_not_be_shallow = 1;
> +			} else {
>  				c->object.flags |= shallow_flag;
> -				commit_list_insert(c, &result);
> -				break;
> +				parent->item->object.flags |= shallow_flag;
>  			}
> +		if (must_not_be_shallow) {
> +			c->object.flags &= ~shallow_flag;
> +			for (parent = c->parents; parent; parent = parent->next)
> +				if (parent->item->object.flags & shallow_flag) {
> +					parent->item->object.flags |= not_shallow_flag;
> +					commit_list_insert(parent->item, &result);
> +				}
> +		} else {
> +			for (parent = c->parents; parent; parent = parent->next)
> +				parent->item->object.flags &= ~shallow_flag;
> +			commit_list_insert(c, &result);
> +		}
>  	}
>  	free_commit_list(not_shallow_list);
>  
> diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
> index 2677cd5faa..12209887fb 100755
> --- a/t/t5500-fetch-pack.sh
> +++ b/t/t5500-fetch-pack.sh
> @@ -904,6 +904,25 @@ test_expect_success 'shallow since with commit graph and already-seen commit' '
>  	)
>  '
>  
> +test_expect_success 'clone shallow since all borders reachable' '
> +	test_create_repo shallow-since-all-borders-reachable &&
> +	(
> +	rm -rf shallow123 &&
> +	cd shallow-since-all-borders-reachable &&
> +	GIT_COMMITTER_DATE="2025-08-19 12:34:56" git commit --allow-empty -m one &&
> +	GIT_COMMITTER_DATE="2025-08-20 12:34:56" git switch -c branch &&
> +	GIT_COMMITTER_DATE="2025-08-21 12:34:56" git commit --allow-empty -m two &&
> +	GIT_COMMITTER_DATE="2025-08-22 12:34:56" git commit --allow-empty -m three &&
> +	GIT_COMMITTER_DATE="2025-08-23 12:34:56" git switch main &&
> +	GIT_COMMITTER_DATE="2025-08-24 12:34:56" git merge branch --no-ff &&
> +	GIT_COMMITTER_DATE="2025-08-26 12:34:56" git clone --shallow-since "2025-08-21 12:34:56" "file://$(pwd)/." ../shallow123 &&
> +	cd ../shallow123 &&
> +	echo "Shallow borders:" &&
> +	cat .git/shallow &&
> +	$(for commit in $(cat .git/shallow); do git rev-list $commit 1>/dev/null || exit 1; done)
> +	)
> +'
> +
>  test_expect_success 'shallow clone exclude tag two' '
>  	test_create_repo shallow-exclude &&
>  	(
>
> base-commit: debbc87557487aa9a8ed8a35367d17f8b4081c76

Re: [PATCH v2] shallow: set borders which are all reachable after clone shallow since

[Junio C Hamano]

Junio C Hamano <gitster@pobox.com> writes:

>> ...
>> The modified implementation of a generic shallow boundary finder
>> based on rev-list ensures that all shallow border commits are reachable
>> also after being grafted. This is achieved by inspecting all parents
>> of each initial border commit candidate. The border commit candidate
>> is set border only when all its parents wern't on the initial list of
>> candidates. Otherwise the border commit candidate is not set as border
>> however its parents that weren't on the list of candidates are set as
>> borders.
>
> It is a minor point, but there are "boundary" and "border" used more
> or less interchangeably in the proposed commit log message, and
> would make the readers wonder if there are differences (I do not
> think we use the word "border" anywhere in our documentation).  It
> is minor as we do not have such mixture in the end-user facing part
> of the documentation with this patch.
>
> I'll let those (cc'ed) who may be more familiar with, or, at least
> have more code than I have in, the shallow infrastructure to comment
> on the way the updated code uses the revision machinery.

After this exchange, the topic has been dormant for almost full two
months.  As I do not deal with shallow clones myself, even though I
understand that some folks rely on it working, I'd really prefer to
see somebody who are familiar with the underlying logic to review
this patch if we were to move forward with it.

Thanks.

Re: [PATCH v2] shallow: set borders which are all reachable after clone shallow since

[Samo Pogačnik]

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On Tue, 2026-01-20 at 12:59 -0800, Junio C Hamano wrote:
> Junio C Hamano <gitster@pobox.com> writes:
> 
> > > ...
> > > The modified implementation of a generic shallow boundary finder
> > > based on rev-list ensures that all shallow border commits are reachable
> > > also after being grafted. This is achieved by inspecting all parents
> > > of each initial border commit candidate. The border commit candidate
> > > is set border only when all its parents wern't on the initial list of
> > > candidates. Otherwise the border commit candidate is not set as border
> > > however its parents that weren't on the list of candidates are set as
> > > borders.
> > 
> > It is a minor point, but there are "boundary" and "border" used more
> > or less interchangeably in the proposed commit log message, and
> > would make the readers wonder if there are differences (I do not
> > think we use the word "border" anywhere in our documentation).  It
> > is minor as we do not have such mixture in the end-user facing part
> > of the documentation with this patch.
> > 
> > I'll let those (cc'ed) who may be more familiar with, or, at least
> > have more code than I have in, the shallow infrastructure to comment
> > on the way the updated code uses the revision machinery.
> 
> After this exchange, the topic has been dormant for almost full two
> months.  As I do not deal with shallow clones myself, even though I
> understand that some folks rely on it working, I'd really prefer to
> see somebody who are familiar with the underlying logic to review
> this patch if we were to move forward with it.
> 

I’m currently rewriting the patch and the commit message trying to
address the boundary/border dilemma. I hope to be able to send a new
version by the end of this week.

Best regards,
Samo

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Re: [PATCH v2] shallow: set borders which are all reachable after clone shallow since

[Samo Pogačnik]

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On Wed, 2026-01-28 at 05:23 +0100, Samo Pogačnik wrote:
> On Tue, 2026-01-20 at 12:59 -0800, Junio C Hamano wrote:
> > Junio C Hamano <gitster@pobox.com> writes:
> > 
> > > > ...
> > > > The modified implementation of a generic shallow boundary finder
> > > > based on rev-list ensures that all shallow border commits are reachable
> > > > also after being grafted. This is achieved by inspecting all parents
> > > > of each initial border commit candidate. The border commit candidate
> > > > is set border only when all its parents wern't on the initial list of
> > > > candidates. Otherwise the border commit candidate is not set as border
> > > > however its parents that weren't on the list of candidates are set as
> > > > borders.
> > > 
> > > It is a minor point, but there are "boundary" and "border" used more
> > > or less interchangeably in the proposed commit log message, and
> > > would make the readers wonder if there are differences (I do not
> > > think we use the word "border" anywhere in our documentation).  It
> > > is minor as we do not have such mixture in the end-user facing part
> > > of the documentation with this patch.
> > > 
> > > I'll let those (cc'ed) who may be more familiar with, or, at least
> > > have more code than I have in, the shallow infrastructure to comment
> > > on the way the updated code uses the revision machinery.
> > 
> > After this exchange, the topic has been dormant for almost full two
> > months.  As I do not deal with shallow clones myself, even though I
> > understand that some folks rely on it working, I'd really prefer to
> > see somebody who are familiar with the underlying logic to review
> > this patch if we were to move forward with it.
> > 
> 
> I’m currently rewriting the patch and the commit message trying to
> address the boundary/border dilemma. I hope to be able to send a new
> version by the end of this week.
> 

I posted a new version of patch '[PATCH v3] shallow: ensure all boundary commits
are reachable with --shallow-since' on 31st of January. I hope you've seen it.

thanks, Samo

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Re: [PATCH v2] shallow: set borders which are all reachable after clone shallow since

[Junio C Hamano]

Samo Pogačnik <samo_pogacnik@t-2.net> writes:

> On Wed, 2026-01-28 at 05:23 +0100, Samo Pogačnik wrote:
>> On Tue, 2026-01-20 at 12:59 -0800, Junio C Hamano wrote:
>> ...
>> > After this exchange, the topic has been dormant for almost full two
>> > months.  As I do not deal with shallow clones myself, even though I
>> > understand that some folks rely on it working, I'd really prefer to
>> > see somebody who are familiar with the underlying logic to review
>> > this patch if we were to move forward with it.
>> > 
>> 
>> I’m currently rewriting the patch and the commit message trying to
>> address the boundary/border dilemma. I hope to be able to send a new
>> version by the end of this week.
>
> I posted a new version of patch '[PATCH v3] shallow: ensure all boundary commits
> are reachable with --shallow-since' on 31st of January. I hope you've seen it.
>
> thanks, Samo

For those of you on the original CC: list taken from v2 review
thread, who may be more qualified to review this topic than I am,
the v3 is found at:

  https://lore.kernel.org/git/pull.2107.v3.git.git.1769876930544.gitgitgadget@gmail.com/

Thanks.

Re: [PATCH v2] shallow: set borders which are all reachable after clone shallow since

[Samo Pogačnik]

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On Fri, 2026-02-06 at 21:19 -0800, Junio C Hamano wrote:
> Samo Pogačnik <samo_pogacnik@t-2.net> writes:
> 
> > On Wed, 2026-01-28 at 05:23 +0100, Samo Pogačnik wrote:
> > > On Tue, 2026-01-20 at 12:59 -0800, Junio C Hamano wrote:
> > > ...
> > > > After this exchange, the topic has been dormant for almost full two
> > > > months.  As I do not deal with shallow clones myself, even though I
> > > > understand that some folks rely on it working, I'd really prefer to
> > > > see somebody who are familiar with the underlying logic to review
> > > > this patch if we were to move forward with it.
> > > > 
> > > 
> > > I’m currently rewriting the patch and the commit message trying to
> > > address the boundary/border dilemma. I hope to be able to send a new
> > > version by the end of this week.
> > 
> > I posted a new version of patch '[PATCH v3] shallow: ensure all boundary
> > commits
> > are reachable with --shallow-since' on 31st of January. I hope you've seen
> > it.
> > 
> > thanks, Samo
> 
> For those of you on the original CC: list taken from v2 review
> thread, who may be more qualified to review this topic than I am,
> the v3 is found at:
> 
>  
> https://lore.kernel.org/git/pull.2107.v3.git.git.1769876930544.gitgitgadget@gmail.com/
> 

Could you please check this correction.

Thanks, Samo


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[PATCH v3] shallow: ensure all boundary commits are reachable with --shallow-since

[Samo Pogačnik via GitGitGadget]

From: =?UTF-8?q?Samo=20Poga=C4=8Dnik?= <samo_pogacnik@t-2.net>

When performing a shallow clone based on a date, it is possible for some
declared shallow boundary commits to be unreachable.

The original implementation of the generic shallow boundary finder based
on rev-list marks a commit (from the initial list of boundary candidates)
as shallow as soon as it finds one parent that is not in the initial
candidate list. This can result in a successful shallow clone where some
declared boundary commits are not reachable and therefore do not exist
in the cloned repository.

In such cases, the result contradicts the existing code comment, which
correctly states that boundary commit candidates with a parent in the
same candidate list must not be considered boundary commits.

The added test case 'clone shallow-since all shallows reachable' exposes
the problem. For example:

0. Original repository
   Graph:
   *   e5fbe33 (HEAD -> main) Apr_4th_13:14:15
   |\
   | * 72f5b73 (branch) Apr_3rd_13:14:15
   |/
   * 0ba76c8 Apr_2nd_13:14:15
   * f58ea3a Apr_1st_13:14:15

1. Clone with --shallow-since="2005-04-03 13:14:15"
   Shallows:
     e5fbe33724032807ab2d8636d4c9161f6716882d
     72f5b73c5fec9a728adc42c23de1b87bb5b3ab16
   Graph:
     * e5fbe33 (grafted, HEAD -> main, ...) Apr_4th_13:14:15

   Note that the second shallow commit,
   72f5b73c5fec9a728adc42c23de1b87bb5b3ab16,
   is not reachable.

Update the generic shallow boundary finder to ensure that all shallow
boundary commits are reachable. This is done by inspecting all parents of
each initial boundary candidate. A candidate is marked shallow only if
all of its parents are not in the initial candidate list. Otherwise, the
candidate itself is not marked shallow, but its parents that are not in
the candidate list are marked as boundary commits instead.

With the same example, the corrected behavior results in:

1. Clone with --shallow-since="2005-04-03 13:14:15"
   Shallows:
     72f5b73c5fec9a728adc42c23de1b87bb5b3ab16
     0ba76c8b72273477b59026bea93fcc792bf48747
   Graph:
     *   e5fbe33 (HEAD -> main, ...) Apr_4th_13:14:15
     |\
     | * 72f5b73 (grafted) Apr_3rd_13:14:15
     * 0ba76c8 (grafted) Apr_2nd_13:14:15

Signed-off-by: Samo Pogačnik <samo_pogacnik@t-2.net>
---
    Fixed --shallow-since generating descendant borders
    
    When shallow cloning based on a date, it happens that a list of commits
    is received, where some of the list border commits actually descend one
    from another. In such cases borders need to be expanded by additional
    parents and excluding the child as border.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2107%2Fspog%2Ffix-shallow-since-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2107/spog/fix-shallow-since-v3
Pull-Request: https://github.com/git/git/pull/2107

Range-diff vs v2:

 1:  479692c386 ! 1:  34df169b67 shallow: set borders which are all reachable after clone shallow since
     @@ Metadata
      Author: Samo Pogačnik <samo_pogacnik@t-2.net>
      
       ## Commit message ##
     -    shallow: set borders which are all reachable after clone shallow since
     +    shallow: ensure all boundary commits are reachable with --shallow-since
      
     -    When shallow cloning based on a date, it happens that not all
     -    shallow border commits are reachable.
     +    When performing a shallow clone based on a date, it is possible for some
     +    declared shallow boundary commits to be unreachable.
      
     -    Original implementation of a generic shallow boundary finder
     -    based on rev-list sets a commit (from the initial list of border
     -    commit candidates) to be the border commit as soon as it finds one
     -    of its parentis that wasn't on the list of initial candidates. This
     -    results in a successful shallow clone, where some of its declared
     -    border commits may not be reachable and they would not actually exist
     -    in the cloned repository. Thus the result may contradict existing
     -    comment in the code, which correctly states that such commmit should
     -    not be considered border.
     +    The original implementation of the generic shallow boundary finder based
     +    on rev-list marks a commit (from the initial list of boundary candidates)
     +    as shallow as soon as it finds one parent that is not in the initial
     +    candidate list. This can result in a successful shallow clone where some
     +    declared boundary commits are not reachable and therefore do not exist
     +    in the cloned repository.
      
     -    One can inspect such case by running the added test scenario:
     -    - 'clone shallow since all borders reachable'
     +    In such cases, the result contradicts the existing code comment, which
     +    correctly states that boundary commit candidates with a parent in the
     +    same candidate list must not be considered boundary commits.
      
     -    The modified implementation of a generic shallow boundary finder
     -    based on rev-list ensures that all shallow border commits are reachable
     -    also after being grafted. This is achieved by inspecting all parents
     -    of each initial border commit candidate. The border commit candidate
     -    is set border only when all its parents wern't on the initial list of
     -    candidates. Otherwise the border commit candidate is not set as border
     -    however its parents that weren't on the list of candidates are set as
     -    borders.
     +    The added test case 'clone shallow-since all shallows reachable' exposes
     +    the problem. For example:
     +
     +    0. Original repository
     +       Graph:
     +       *   e5fbe33 (HEAD -> main) Apr_4th_13:14:15
     +       |\
     +       | * 72f5b73 (branch) Apr_3rd_13:14:15
     +       |/
     +       * 0ba76c8 Apr_2nd_13:14:15
     +       * f58ea3a Apr_1st_13:14:15
     +
     +    1. Clone with --shallow-since="2005-04-03 13:14:15"
     +       Shallows:
     +         e5fbe33724032807ab2d8636d4c9161f6716882d
     +         72f5b73c5fec9a728adc42c23de1b87bb5b3ab16
     +       Graph:
     +         * e5fbe33 (grafted, HEAD -> main, ...) Apr_4th_13:14:15
     +
     +       Note that the second shallow commit,
     +       72f5b73c5fec9a728adc42c23de1b87bb5b3ab16,
     +       is not reachable.
     +
     +    Update the generic shallow boundary finder to ensure that all shallow
     +    boundary commits are reachable. This is done by inspecting all parents of
     +    each initial boundary candidate. A candidate is marked shallow only if
     +    all of its parents are not in the initial candidate list. Otherwise, the
     +    candidate itself is not marked shallow, but its parents that are not in
     +    the candidate list are marked as boundary commits instead.
     +
     +    With the same example, the corrected behavior results in:
     +
     +    1. Clone with --shallow-since="2005-04-03 13:14:15"
     +       Shallows:
     +         72f5b73c5fec9a728adc42c23de1b87bb5b3ab16
     +         0ba76c8b72273477b59026bea93fcc792bf48747
     +       Graph:
     +         *   e5fbe33 (HEAD -> main, ...) Apr_4th_13:14:15
     +         |\
     +         | * 72f5b73 (grafted) Apr_3rd_13:14:15
     +         * 0ba76c8 (grafted) Apr_2nd_13:14:15
      
          Signed-off-by: Samo Pogačnik <samo_pogacnik@t-2.net>
      
       ## shallow.c ##
     +@@ shallow.c: static void show_commit(struct commit *commit, void *data)
     + }
     + 
     + /*
     +- * Given rev-list arguments, run rev-list. All reachable commits
     +- * except border ones are marked with not_shallow_flag. Border commits
     +- * are marked with shallow_flag. The list of border/shallow commits
     +- * are also returned.
     ++ * Given rev-list arguments, run rev-list. All reachable commits except
     ++ * shallow boundary commits are marked with not_shallow_flag.
     ++ * Returned is a list of boundary commits marked with shallow_flag only.
     +  */
     + struct commit_list *get_shallow_commits_by_rev_list(struct strvec *argv,
     + 						    int shallow_flag,
      @@ shallow.c: struct commit_list *get_shallow_commits_by_rev_list(struct strvec *argv,
     - 	 * commit A is processed first, then commit B, whose parent is
     - 	 * A, later. If NOT_SHALLOW on A is cleared at step 1, B
     - 	 * itself is considered border at step 2, which is incorrect.
     + 	if (!not_shallow_list)
     + 		die("no commits selected for shallow requests");
     + 
     +-	/* Mark all reachable commits as NOT_SHALLOW */
     ++	/* Mark all reachable (listed) commits as NOT_SHALLOW */
     + 	for (p = not_shallow_list; p; p = p->next)
     + 		p->item->object.flags |= not_shallow_flag;
     + 
     + 	/*
     +-	 * mark border commits SHALLOW + NOT_SHALLOW.
     +-	 * We cannot clear NOT_SHALLOW right now. Imagine border
     +-	 * commit A is processed first, then commit B, whose parent is
     +-	 * A, later. If NOT_SHALLOW on A is cleared at step 1, B
     +-	 * itself is considered border at step 2, which is incorrect.
     ++	 * Mark shallow commits from the list as SHALLOW + NOT_SHALLOW.
     ++	 * Do not clear NOT_SHALLOW flags immediately. Consider two listed
     ++	 * commits, B and its parent A, where A is shallow. If A is processed
     ++	 * first and its NOT_SHALLOW flag is cleared immediately, B would later
     ++	 * be incorrectly marked SHALLOW when processed.
     ++	 *
     ++	 * Also, listed commits may have multiple parents, and not all parents
     ++	 * are necessarily listed (as they were not all traversed into the
     ++	 * not_shallow_list from the revs in the first place — not marked
     ++	 * NOT_SHALLOW). Therefore:
      +	 *
     -+	 * We must also consider that B has multiple parents which may
     -+	 * not all be marked NOT_SHALLOW (as they weren't traversed into
     -+	 * the not_shallow_list from revs in the first place). Because of
     -+	 * that an additional step is required to reconsider B as border.
     -+	 * A commit from the not_shallow_list is considered border only
     -+	 * when ALL its parents weren't on the not_shallow_list.
     -+	 * When one or more parents of a commit from the not_shellow_list
     -+	 * also come from that list, the commit is not considered border,
     -+	 * but its non-listed parents are considered border commits.
     ++	 * - A listed commit is marked SHALLOW only if none of its parents are
     ++	 *   listed.
     ++	 * - If at least one parent of a listed commit is also listed, the
     ++	 *   commit itself is not marked SHALLOW; however, any of its non-listed
     ++	 *   parents are marked SHALLOW.
      +	 *
     -+	 * The general processing goes like this:
     -+	 * 1. Above we've painted the whole not_shallow_list of commits
     -+	 *    NOT_SHALLOW.
     -+	 * 2. For each commit from the not_shallow_list (the code below)
     -+	 *    we paint SHALLOW this commit and its parent for all its
     -+	 *    parents that had not yet been painted NOT_SHALLOW.
     -+	 * 3. Commits with all parents being painted only SHALLOW remain
     -+	 *    shallow and are being added to result list.
     -+	 * 4. Commits without all parents being painted only SHALLOW are
     -+	 *    being excluded as borders, however their parents painted only
     -+	 *    SHALLOW are being added to the result borders list.
     ++	 * Processing overview:
     ++	 * 1. All listed commits have already been marked NOT_SHALLOW are not
     ++	 *    cleared until all shallow commits have been identified.
     ++	 *
     ++	 * 2. For each listed commit:
     ++	 *    - Mark the commit SHALLOW if it has any parent that is not listed.
     ++	 *    - Mark all non-listed parents as SHALLOW.
     ++	 *    - If the commit has at least one listed parent, it is excluded
     ++	 *      from the shallow result; however its parents marked only SHALLOW
     ++	 *      are added instead.
     ++	 *    - If all parents are marked only SHALLOW, the commit remains SHALLOW
     ++	 *      and is added to the shallow result.
       	 */
       	for (p = not_shallow_list; p; p = p->next) {
       		struct commit *c = p->item;
     @@ shallow.c: struct commit_list *get_shallow_commits_by_rev_list(struct strvec *ar
       		if (repo_parse_commit(the_repository, c))
       			die("unable to parse commit %s",
       			    oid_to_hex(&c->object.oid));
     ++		if (!c->parents)
     ++			continue;
       
       		for (parent = c->parents; parent; parent = parent->next)
      -			if (!(parent->item->object.flags & not_shallow_flag)) {
     @@ shallow.c: struct commit_list *get_shallow_commits_by_rev_list(struct strvec *ar
      -				break;
      +				parent->item->object.flags |= shallow_flag;
       			}
     ++
      +		if (must_not_be_shallow) {
      +			c->object.flags &= ~shallow_flag;
      +			for (parent = c->parents; parent; parent = parent->next)
     -+				if (parent->item->object.flags & shallow_flag) {
     -+					parent->item->object.flags |= not_shallow_flag;
     ++				if ((parent->item->object.flags & shallow_flag) &&
     ++				    !(parent->item->object.flags & not_shallow_flag))
      +					commit_list_insert(parent->item, &result);
     -+				}
      +		} else {
      +			for (parent = c->parents; parent; parent = parent->next)
      +				parent->item->object.flags &= ~shallow_flag;
     @@ shallow.c: struct commit_list *get_shallow_commits_by_rev_list(struct strvec *ar
       	}
       	free_commit_list(not_shallow_list);
       
     + 	/*
     +-	 * Now we can clean up NOT_SHALLOW on border commits. Having
     ++	 * Now we can clean up NOT_SHALLOW on shallow commits. Having
     + 	 * both flags set can confuse the caller.
     + 	 */
     + 	for (p = result; p; p = p->next) {
      
       ## t/t5500-fetch-pack.sh ##
      @@ t/t5500-fetch-pack.sh: test_expect_success 'shallow since with commit graph and already-seen commit' '
       	)
       '
       
     -+test_expect_success 'clone shallow since all borders reachable' '
     -+	test_create_repo shallow-since-all-borders-reachable &&
     ++test_expect_success 'clone shallow-since all shallows reachable' '
     ++	test_create_repo shallow-since-all-shallows-reachable &&
      +	(
     -+	rm -rf shallow123 &&
     -+	cd shallow-since-all-borders-reachable &&
     -+	GIT_COMMITTER_DATE="2025-08-19 12:34:56" git commit --allow-empty -m one &&
     -+	GIT_COMMITTER_DATE="2025-08-20 12:34:56" git switch -c branch &&
     -+	GIT_COMMITTER_DATE="2025-08-21 12:34:56" git commit --allow-empty -m two &&
     -+	GIT_COMMITTER_DATE="2025-08-22 12:34:56" git commit --allow-empty -m three &&
     -+	GIT_COMMITTER_DATE="2025-08-23 12:34:56" git switch main &&
     -+	GIT_COMMITTER_DATE="2025-08-24 12:34:56" git merge branch --no-ff &&
     -+	GIT_COMMITTER_DATE="2025-08-26 12:34:56" git clone --shallow-since "2025-08-21 12:34:56" "file://$(pwd)/." ../shallow123 &&
     -+	cd ../shallow123 &&
     -+	echo "Shallow borders:" &&
     -+	cat .git/shallow &&
     -+	$(for commit in $(cat .git/shallow); do git rev-list $commit 1>/dev/null || exit 1; done)
     ++		rm -rf shallow123 &&
     ++		cd shallow-since-all-shallows-reachable &&
     ++		GIT_COMMITTER_DATE="2005-04-01 13:14:15" git commit --allow-empty -m Apr_1st &&
     ++		GIT_COMMITTER_DATE="2005-04-02 13:14:15" git commit --allow-empty -m Apr_2nd &&
     ++		GIT_COMMITTER_DATE="2005-04-03 13:14:15" git switch -c branch &&
     ++		GIT_COMMITTER_DATE="2005-04-03 13:14:15" git commit --allow-empty -m Apr_3rd &&
     ++		GIT_COMMITTER_DATE="2005-04-04 13:14:15" git switch main &&
     ++		GIT_COMMITTER_DATE="2005-04-04 13:14:15" git merge branch --no-ff -m Apr_4th &&
     ++		git clone --shallow-since "2005-04-03 13:14:15" "file://$(pwd)/." ../shallow123 &&
     ++		cd ../shallow123 &&
     ++		for commit in $(cat .git/shallow 2> /dev/null)
     ++		do
     ++			git rev-list $commit 1>/dev/null || exit 1
     ++		done
      +	)
      +'
      +


 shallow.c             | 67 ++++++++++++++++++++++++++++++++++---------
 t/t5500-fetch-pack.sh | 20 +++++++++++++
 2 files changed, 73 insertions(+), 14 deletions(-)

diff --git a/shallow.c b/shallow.c
index 55b9cd9d3f..cd99e5777f 100644
--- a/shallow.c
+++ b/shallow.c
@@ -208,10 +208,9 @@ static void show_commit(struct commit *commit, void *data)
 }
 
 /*
- * Given rev-list arguments, run rev-list. All reachable commits
- * except border ones are marked with not_shallow_flag. Border commits
- * are marked with shallow_flag. The list of border/shallow commits
- * are also returned.
+ * Given rev-list arguments, run rev-list. All reachable commits except
+ * shallow boundary commits are marked with not_shallow_flag.
+ * Returned is a list of boundary commits marked with shallow_flag only.
  */
 struct commit_list *get_shallow_commits_by_rev_list(struct strvec *argv,
 						    int shallow_flag,
@@ -241,36 +240,76 @@ struct commit_list *get_shallow_commits_by_rev_list(struct strvec *argv,
 	if (!not_shallow_list)
 		die("no commits selected for shallow requests");
 
-	/* Mark all reachable commits as NOT_SHALLOW */
+	/* Mark all reachable (listed) commits as NOT_SHALLOW */
 	for (p = not_shallow_list; p; p = p->next)
 		p->item->object.flags |= not_shallow_flag;
 
 	/*
-	 * mark border commits SHALLOW + NOT_SHALLOW.
-	 * We cannot clear NOT_SHALLOW right now. Imagine border
-	 * commit A is processed first, then commit B, whose parent is
-	 * A, later. If NOT_SHALLOW on A is cleared at step 1, B
-	 * itself is considered border at step 2, which is incorrect.
+	 * Mark shallow commits from the list as SHALLOW + NOT_SHALLOW.
+	 * Do not clear NOT_SHALLOW flags immediately. Consider two listed
+	 * commits, B and its parent A, where A is shallow. If A is processed
+	 * first and its NOT_SHALLOW flag is cleared immediately, B would later
+	 * be incorrectly marked SHALLOW when processed.
+	 *
+	 * Also, listed commits may have multiple parents, and not all parents
+	 * are necessarily listed (as they were not all traversed into the
+	 * not_shallow_list from the revs in the first place — not marked
+	 * NOT_SHALLOW). Therefore:
+	 *
+	 * - A listed commit is marked SHALLOW only if none of its parents are
+	 *   listed.
+	 * - If at least one parent of a listed commit is also listed, the
+	 *   commit itself is not marked SHALLOW; however, any of its non-listed
+	 *   parents are marked SHALLOW.
+	 *
+	 * Processing overview:
+	 * 1. All listed commits have already been marked NOT_SHALLOW are not
+	 *    cleared until all shallow commits have been identified.
+	 *
+	 * 2. For each listed commit:
+	 *    - Mark the commit SHALLOW if it has any parent that is not listed.
+	 *    - Mark all non-listed parents as SHALLOW.
+	 *    - If the commit has at least one listed parent, it is excluded
+	 *      from the shallow result; however its parents marked only SHALLOW
+	 *      are added instead.
+	 *    - If all parents are marked only SHALLOW, the commit remains SHALLOW
+	 *      and is added to the shallow result.
 	 */
 	for (p = not_shallow_list; p; p = p->next) {
 		struct commit *c = p->item;
 		struct commit_list *parent;
+		int must_not_be_shallow = 0;
 
 		if (repo_parse_commit(the_repository, c))
 			die("unable to parse commit %s",
 			    oid_to_hex(&c->object.oid));
+		if (!c->parents)
+			continue;
 
 		for (parent = c->parents; parent; parent = parent->next)
-			if (!(parent->item->object.flags & not_shallow_flag)) {
+			if (parent->item->object.flags & not_shallow_flag) {
+				must_not_be_shallow = 1;
+			} else {
 				c->object.flags |= shallow_flag;
-				commit_list_insert(c, &result);
-				break;
+				parent->item->object.flags |= shallow_flag;
 			}
+
+		if (must_not_be_shallow) {
+			c->object.flags &= ~shallow_flag;
+			for (parent = c->parents; parent; parent = parent->next)
+				if ((parent->item->object.flags & shallow_flag) &&
+				    !(parent->item->object.flags & not_shallow_flag))
+					commit_list_insert(parent->item, &result);
+		} else {
+			for (parent = c->parents; parent; parent = parent->next)
+				parent->item->object.flags &= ~shallow_flag;
+			commit_list_insert(c, &result);
+		}
 	}
 	free_commit_list(not_shallow_list);
 
 	/*
-	 * Now we can clean up NOT_SHALLOW on border commits. Having
+	 * Now we can clean up NOT_SHALLOW on shallow commits. Having
 	 * both flags set can confuse the caller.
 	 */
 	for (p = result; p; p = p->next) {
diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
index 2677cd5faa..44e274281a 100755
--- a/t/t5500-fetch-pack.sh
+++ b/t/t5500-fetch-pack.sh
@@ -904,6 +904,26 @@ test_expect_success 'shallow since with commit graph and already-seen commit' '
 	)
 '
 
+test_expect_success 'clone shallow-since all shallows reachable' '
+	test_create_repo shallow-since-all-shallows-reachable &&
+	(
+		rm -rf shallow123 &&
+		cd shallow-since-all-shallows-reachable &&
+		GIT_COMMITTER_DATE="2005-04-01 13:14:15" git commit --allow-empty -m Apr_1st &&
+		GIT_COMMITTER_DATE="2005-04-02 13:14:15" git commit --allow-empty -m Apr_2nd &&
+		GIT_COMMITTER_DATE="2005-04-03 13:14:15" git switch -c branch &&
+		GIT_COMMITTER_DATE="2005-04-03 13:14:15" git commit --allow-empty -m Apr_3rd &&
+		GIT_COMMITTER_DATE="2005-04-04 13:14:15" git switch main &&
+		GIT_COMMITTER_DATE="2005-04-04 13:14:15" git merge branch --no-ff -m Apr_4th &&
+		git clone --shallow-since "2005-04-03 13:14:15" "file://$(pwd)/." ../shallow123 &&
+		cd ../shallow123 &&
+		for commit in $(cat .git/shallow 2> /dev/null)
+		do
+			git rev-list $commit 1>/dev/null || exit 1
+		done
+	)
+'
+
 test_expect_success 'shallow clone exclude tag two' '
 	test_create_repo shallow-exclude &&
 	(

base-commit: debbc87557487aa9a8ed8a35367d17f8b4081c76
-- 
gitgitgadget