[PATCH] fetch-pack: approximate no_dependents with filter

[PATCH] fetch-pack: approximate no_dependents with filter

[Jonathan Tan]

Whenever a lazy fetch is performed for a tree object, any trees and
blobs it directly or indirectly references will be fetched as well.
There is a "no_dependents" argument in struct fetch_pack_args that
indicates that objects that the wanted object references need not be
sent, but it currently has no effect other than to inhibit usage of
object flags.

Extend the "no_dependents" argument to also exclude sending of objects
as much as the current protocol allows: when fetching a tree, all trees
it references will be sent (but not the blobs), and when fetching a
blob, it will still be sent. (If this mechanism is used to fetch a
commit or any other non-blob object, all referenced objects, except
blobs, will be sent.) The client neither needs to know or specify the
type of each object it wants.

The necessary code change is done in fetch_pack() instead of somewhere
closer to where the "filter" instruction is written to the wire so that
only one part of the code needs to be changed in order for users of all
protocol versions to benefit from this optimization.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
This was prompted by a user at $DAY_JOB who had a partial clone
excluding trees, and had a workflow that only required tree objects (and
not blobs).

This will hopefully make partial clones excluding trees (with the
"tree:0" filter) a bit better, in that if an operation requires only
trees to be inspected, the required download is much smaller.
---
 fetch-pack.c             | 14 ++++++++++++++
 fetch-pack.h             |  7 +++++++
 t/t0410-partial-clone.sh | 41 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+)

diff --git a/fetch-pack.c b/fetch-pack.c
index 88a078e9b..c25b0f54c 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1598,6 +1598,20 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 	if (nr_sought)
 		nr_sought = remove_duplicates_in_refs(sought, nr_sought);
 
+	if (args->no_dependents && !args->filter_options.choice) {
+		/*
+		 * The protocol does not support requesting that only the
+		 * wanted objects be sent, so approximate this by setting a
+		 * "blob:none" filter if no filter is already set. This works
+		 * for all object types: note that wanted blobs will still be
+		 * sent because they are directly specified as a "want".
+		 *
+		 * NEEDSWORK: Add an option in the protocol to request that
+		 * only the wanted objects be sent, and implement it.
+		 */
+		parse_list_objects_filter(&args->filter_options, "blob:none");
+	}
+
 	if (!ref) {
 		packet_flush(fd[1]);
 		die(_("no matching remote head"));
diff --git a/fetch-pack.h b/fetch-pack.h
index 5b6e86880..43ec344d9 100644
--- a/fetch-pack.h
+++ b/fetch-pack.h
@@ -43,6 +43,13 @@ struct fetch_pack_args {
 	unsigned from_promisor:1;
 
 	/*
+	 * Attempt to fetch only the wanted objects, and not any objects
+	 * referred to by them. Due to protocol limitations, extraneous
+	 * objects may still be included. (When fetching non-blob
+	 * objects, only blobs are excluded; when fetching a blob, the
+	 * blob itself will still be sent. The client does not need to
+	 * know whether a wanted object is a blob or not.)
+	 *
 	 * If 1, fetch_pack() will also not modify any object flags.
 	 * This allows fetch_pack() to safely be called by any function,
 	 * regardless of which object flags it uses (if any).
diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index 128130066..08a0c3651 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -170,6 +170,47 @@ test_expect_success 'fetching of missing objects' '
 	git verify-pack --verbose "$IDX" | grep "$HASH"
 '
 
+test_expect_success 'fetching of missing blobs works' '
+	rm -rf server repo &&
+	test_create_repo server &&
+	test_commit -C server foo &&
+	git -C server repack -a -d --write-bitmap-index &&
+
+	git clone "file://$(pwd)/server" repo &&
+	git hash-object repo/foo.t >blobhash &&
+	rm -rf repo/.git/objects/* &&
+
+	git -C server config uploadpack.allowanysha1inwant 1 &&
+	git -C server config uploadpack.allowfilter 1 &&
+	git -C repo config core.repositoryformatversion 1 &&
+	git -C repo config extensions.partialclone "origin" &&
+
+	git -C repo cat-file -p $(cat blobhash)
+'
+
+test_expect_success 'fetching of missing trees does not fetch blobs' '
+	rm -rf server repo &&
+	test_create_repo server &&
+	test_commit -C server foo &&
+	git -C server repack -a -d --write-bitmap-index &&
+
+	git clone "file://$(pwd)/server" repo &&
+	git -C repo rev-parse foo^{tree} >treehash &&
+	git hash-object repo/foo.t >blobhash &&
+	rm -rf repo/.git/objects/* &&
+
+	git -C server config uploadpack.allowanysha1inwant 1 &&
+	git -C server config uploadpack.allowfilter 1 &&
+	git -C repo config core.repositoryformatversion 1 &&
+	git -C repo config extensions.partialclone "origin" &&
+	git -C repo cat-file -p $(cat treehash) &&
+
+	# Ensure that the tree, but not the blob, is fetched
+	git -C repo rev-list --objects --missing=print $(cat treehash) >objects &&
+	grep "^$(cat treehash)" objects &&
+	grep "^[?]$(cat blobhash)" objects
+'
+
 test_expect_success 'rev-list stops traversal at missing and promised commit' '
 	rm -rf repo &&
 	test_create_repo repo &&
-- 
2.19.0.444.g18242da7ef-goog

Re: [PATCH] fetch-pack: approximate no_dependents with filter

[Junio C Hamano]

Jonathan Tan <jonathantanmy@google.com> writes:

> Whenever a lazy fetch is performed for a tree object, any trees and
> blobs it directly or indirectly references will be fetched as well.
> There is a "no_dependents" argument in struct fetch_pack_args that
> indicates that objects that the wanted object references need not be
> sent, but it currently has no effect other than to inhibit usage of
> object flags.
>
> Extend the "no_dependents" argument to also exclude sending of objects
> as much as the current protocol allows: when fetching a tree, all trees
> it references will be sent (but not the blobs), and when fetching a
> blob, it will still be sent. (If this mechanism is used to fetch a
> commit or any other non-blob object, all referenced objects, except
> blobs, will be sent.) The client neither needs to know or specify the
> type of each object it wants.
>
> The necessary code change is done in fetch_pack() instead of somewhere
> closer to where the "filter" instruction is written to the wire so that
> only one part of the code needs to be changed in order for users of all
> protocol versions to benefit from this optimization.

It is very clear how you are churning the code, but it is utterly
unclear from the description what you perceived as a problem and why
this change is a good (if not the best) solution for that problem,
at least to me.

After reading the above description, I cannot shake the feeling that
this is tied too strongly to the tree:0 use case?  Does it help
other use cases (e.g. would it be useful or harmful if a lazy clone
was done to exclude blobs that are larger than certain threshold, or
objects of all types that are not referenced by commits younger than
certain threshold)?

Re: [PATCH] fetch-pack: approximate no_dependents with filter

[Jonathan Tan]

> It is very clear how you are churning the code, but it is utterly
> unclear from the description what you perceived as a problem and why
> this change is a good (if not the best) solution for that problem,
> at least to me.

Firstly, thanks for your comments and questions - it's sometimes hard
for me to think of the questions someone else would ask when reading one
of my patches. I have tried to rewrite the commit message (you can see
it at the end of this e-mail) following your questions.

The new paragraph 1 addresses what I perceive as a problem, and the new
paragraph 2 addresses the ideal and partial solution.

> After reading the above description, I cannot shake the feeling that
> this is tied too strongly to the tree:0 use case?  Does it help
> other use cases (e.g. would it be useful or harmful if a lazy clone
> was done to exclude blobs that are larger than certain threshold, or
> objects of all types that are not referenced by commits younger than
> certain threshold)?

Yes, it is solely for the tree:0 use case. But it doesn't hurt other use
cases, as I have explained in new paragraph 3.

I have retained old paragraph 3 as new paragraph 4, and removed old
paragraph 2 as it mostly duplicates the comments in the code. New commit
message follows:

[start commit message]

fetch-pack: exclude blobs when lazy-fetching trees

A partial clone with missing trees can be obtained using "git clone
--filter=tree:none <repo>". In such a repository, when a tree needs to
be lazily fetched, any tree or blob it directly or indirectly references
is fetched as well, regardless of whether the original command required
those objects, or if the local repository already had some of them.

This is because the fetch protocol, which the lazy fetch uses, does not
allow clients to request that only the wanted objects be sent, which
would be the ideal solution. This patch implements a partial solution:
specify the "blob:none" filter, somewhat reducing the fetch payload.

This change has no effect when lazily fetching blobs (due to how filters
work). And if lazily fetching a commit (such repositories are difficult
to construct and is not a use case we support very well, but it is
possible), referenced commits and trees are still fetched - only the
blobs are not fetched.

The necessary code change is done in fetch_pack() instead of somewhere
closer to where the "filter" instruction is written to the wire so that
only one part of the code needs to be changed in order for users of all
protocol versions to benefit from this optimization.

[end commit message]

Re: [PATCH] fetch-pack: approximate no_dependents with filter

[Junio C Hamano]

Jonathan Tan <jonathantanmy@google.com> writes:

> This was prompted by a user at $DAY_JOB who had a partial clone
> excluding trees, and had a workflow that only required tree objects (and
> not blobs).
>
> This will hopefully make partial clones excluding trees (with the
> "tree:0" filter) a bit better, in that if an operation requires only
> trees to be inspected, the required download is much smaller.

This seems to break 5520 and 5616 when merged to 'pu'.  

It seems that merging master to md/filter-trees and then applying
this is sufficient to break 5616.

[PATCH v2 0/2] Lazy fetch bug fix (and feature that reveals it)

[Jonathan Tan]

> This seems to break 5520 and 5616 when merged to 'pu'.  
> 
> It seems that merging master to md/filter-trees and then applying
> this is sufficient to break 5616.

I verified that 5616 is broken on [master + md/filter-trees + my patch],
and after investigation, found a bug in the lazy fetch implementation.
Patch 1 contains a fix, and more information about that bug.

Patch 2 is the original patch, updated with the commit message I
suggested [1] in reply to Junio's comment.

I bundled these patches together because patch 2 (in combination with
certain other commits) reveals the bug that patch 1 fixes, and to make
it easier for others to verify that these patches together pass all
tests when rebased on [master + md/filter-trees] or 'pu' (at least, as
of the time of writing).

[1] https://public-inbox.org/git/20180927183718.89804-1-jonathantanmy@google.com/

Jonathan Tan (2):
  fetch-pack: avoid object flags if no_dependents
  fetch-pack: exclude blobs when lazy-fetching trees

 fetch-pack.c             | 115 +++++++++++++++++++++++++--------------
 fetch-pack.h             |   7 +++
 t/t0410-partial-clone.sh |  41 ++++++++++++++
 3 files changed, 121 insertions(+), 42 deletions(-)

-- 
2.19.0.605.g01d371f741-goog

[PATCH v2 1/2] fetch-pack: avoid object flags if no_dependents

[Jonathan Tan]

When fetch_pack() is invoked as part of another Git command (due to a
lazy fetch from a partial clone, for example), it uses object flags that
may already be used by the outer Git command.

The commit that introduced the lazy fetch feature (88e2f9ed8e
("introduce fetch-object: fetch one promisor object", 2017-12-05)) tried
to avoid this overlap, but it did not avoid it totally. It was
successful in avoiding writing COMPLETE, but did not avoid reading
COMPLETE, and did not avoid writing and reading ALTERNATE.

Ensure that no flags are written or read by fetch_pack() in the case
where it is used to perform a lazy fetch. To do this, it is sufficient
to avoid checking completeness of wanted refs (unnecessary in the case
of lazy fetches), and to avoid negotiation-related work (in the current
implementation, already, no negotiation is performed). After that was
done, the lack of overlap was verified by checking all direct and
indirect usages of COMPLETE and ALTERNATE - that they are read or
written only if no_dependents is false.

There are other possible solutions to this issue:

 (1) Split fetch-pack.{c,h} into a flag-using part and a non-flag-using
     part, and whenever no_dependents is set, only use the
     non-flag-using part.
 (2) Make fetch_pack() be able to be used with arbitrary repository
     objects. fetch_pack() should then create its own repository object
     based on the given repository object, with its own object
     hashtable, so that the flags do not conflict.

(1) is possible but invasive - some functions would need to be split;
and such invasiveness would potentially be unnecessary if we ever were
to need (2) anyway. (2) would be useful if we were to support, say,
submodules that were partial clones themselves, but I don't know when or
if the Git project plans to support those.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 fetch-pack.c | 101 ++++++++++++++++++++++++++++++---------------------
 1 file changed, 59 insertions(+), 42 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 75047a4b2a..b9b1211dda 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -253,8 +253,10 @@ static int find_common(struct fetch_negotiator *negotiator,
 	if (args->stateless_rpc && multi_ack == 1)
 		die(_("--stateless-rpc requires multi_ack_detailed"));
 
-	mark_tips(negotiator, args->negotiation_tips);
-	for_each_cached_alternate(negotiator, insert_one_alternate_object);
+	if (!args->no_dependents) {
+		mark_tips(negotiator, args->negotiation_tips);
+		for_each_cached_alternate(negotiator, insert_one_alternate_object);
+	}
 
 	fetching = 0;
 	for ( ; refs ; refs = refs->next) {
@@ -271,8 +273,12 @@ static int find_common(struct fetch_negotiator *negotiator,
 		 * We use lookup_object here because we are only
 		 * interested in the case we *know* the object is
 		 * reachable and we have already scanned it.
+		 *
+		 * Do this only if args->no_dependents is false (if it is true,
+		 * we cannot trust the object flags).
 		 */
-		if (((o = lookup_object(the_repository, remote->hash)) != NULL) &&
+		if (!args->no_dependents &&
+		    ((o = lookup_object(the_repository, remote->hash)) != NULL) &&
 				(o->flags & COMPLETE)) {
 			continue;
 		}
@@ -710,31 +716,29 @@ static void mark_complete_and_common_ref(struct fetch_negotiator *negotiator,
 
 	oidset_clear(&loose_oid_set);
 
-	if (!args->no_dependents) {
-		if (!args->deepen) {
-			for_each_ref(mark_complete_oid, NULL);
-			for_each_cached_alternate(NULL, mark_alternate_complete);
-			commit_list_sort_by_date(&complete);
-			if (cutoff)
-				mark_recent_complete_commits(args, cutoff);
-		}
+	if (!args->deepen) {
+		for_each_ref(mark_complete_oid, NULL);
+		for_each_cached_alternate(NULL, mark_alternate_complete);
+		commit_list_sort_by_date(&complete);
+		if (cutoff)
+			mark_recent_complete_commits(args, cutoff);
+	}
 
-		/*
-		 * Mark all complete remote refs as common refs.
-		 * Don't mark them common yet; the server has to be told so first.
-		 */
-		for (ref = *refs; ref; ref = ref->next) {
-			struct object *o = deref_tag(the_repository,
-						     lookup_object(the_repository,
-						     ref->old_oid.hash),
-						     NULL, 0);
+	/*
+	 * Mark all complete remote refs as common refs.
+	 * Don't mark them common yet; the server has to be told so first.
+	 */
+	for (ref = *refs; ref; ref = ref->next) {
+		struct object *o = deref_tag(the_repository,
+					     lookup_object(the_repository,
+					     ref->old_oid.hash),
+					     NULL, 0);
 
-			if (!o || o->type != OBJ_COMMIT || !(o->flags & COMPLETE))
-				continue;
+		if (!o || o->type != OBJ_COMMIT || !(o->flags & COMPLETE))
+			continue;
 
-			negotiator->known_common(negotiator,
-						 (struct commit *)o);
-		}
+		negotiator->known_common(negotiator,
+					 (struct commit *)o);
 	}
 
 	save_commit_buffer = old_save_commit_buffer;
@@ -990,11 +994,15 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	if (!server_supports("deepen-relative") && args->deepen_relative)
 		die(_("Server does not support --deepen"));
 
-	mark_complete_and_common_ref(&negotiator, args, &ref);
-	filter_refs(args, &ref, sought, nr_sought);
-	if (everything_local(args, &ref)) {
-		packet_flush(fd[1]);
-		goto all_done;
+	if (!args->no_dependents) {
+		mark_complete_and_common_ref(&negotiator, args, &ref);
+		filter_refs(args, &ref, sought, nr_sought);
+		if (everything_local(args, &ref)) {
+			packet_flush(fd[1]);
+			goto all_done;
+		}
+	} else {
+		filter_refs(args, &ref, sought, nr_sought);
 	}
 	if (find_common(&negotiator, args, fd, &oid, ref) < 0)
 		if (!args->keep_pack)
@@ -1040,7 +1048,7 @@ static void add_shallow_requests(struct strbuf *req_buf,
 	}
 }
 
-static void add_wants(const struct ref *wants, struct strbuf *req_buf)
+static void add_wants(int no_dependents, const struct ref *wants, struct strbuf *req_buf)
 {
 	int use_ref_in_want = server_supports_feature("fetch", "ref-in-want", 0);
 
@@ -1057,8 +1065,12 @@ static void add_wants(const struct ref *wants, struct strbuf *req_buf)
 		 * We use lookup_object here because we are only
 		 * interested in the case we *know* the object is
 		 * reachable and we have already scanned it.
+		 *
+		 * Do this only if args->no_dependents is false (if it is true,
+		 * we cannot trust the object flags).
 		 */
-		if (((o = lookup_object(the_repository, remote->hash)) != NULL) &&
+		if (!no_dependents &&
+		    ((o = lookup_object(the_repository, remote->hash)) != NULL) &&
 		    (o->flags & COMPLETE)) {
 			continue;
 		}
@@ -1155,7 +1167,7 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 	}
 
 	/* add wants */
-	add_wants(wants, &req_buf);
+	add_wants(args->no_dependents, wants, &req_buf);
 
 	if (args->no_dependents) {
 		packet_buf_write(&req_buf, "done");
@@ -1346,16 +1358,21 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				args->deepen = 1;
 
 			/* Filter 'ref' by 'sought' and those that aren't local */
-			mark_complete_and_common_ref(&negotiator, args, &ref);
-			filter_refs(args, &ref, sought, nr_sought);
-			if (everything_local(args, &ref))
-				state = FETCH_DONE;
-			else
+			if (!args->no_dependents) {
+				mark_complete_and_common_ref(&negotiator, args, &ref);
+				filter_refs(args, &ref, sought, nr_sought);
+				if (everything_local(args, &ref))
+					state = FETCH_DONE;
+				else
+					state = FETCH_SEND_REQUEST;
+
+				mark_tips(&negotiator, args->negotiation_tips);
+				for_each_cached_alternate(&negotiator,
+							  insert_one_alternate_object);
+			} else {
+				filter_refs(args, &ref, sought, nr_sought);
 				state = FETCH_SEND_REQUEST;
-
-			mark_tips(&negotiator, args->negotiation_tips);
-			for_each_cached_alternate(&negotiator,
-						  insert_one_alternate_object);
+			}
 			break;
 		case FETCH_SEND_REQUEST:
 			if (send_fetch_request(&negotiator, fd[1], args, ref,
-- 
2.19.0.605.g01d371f741-goog

[PATCH v2 2/2] fetch-pack: exclude blobs when lazy-fetching trees

[Jonathan Tan]

A partial clone with missing trees can be obtained using "git clone
--filter=tree:none <repo>". In such a repository, when a tree needs to
be lazily fetched, any tree or blob it directly or indirectly references
is fetched as well, regardless of whether the original command required
those objects, or if the local repository already had some of them.

This is because the fetch protocol, which the lazy fetch uses, does not
allow clients to request that only the wanted objects be sent, which
would be the ideal solution. This patch implements a partial solution:
specify the "blob:none" filter, somewhat reducing the fetch payload.

This change has no effect when lazily fetching blobs (due to how filters
work). And if lazily fetching a commit (such repositories are difficult
to construct and is not a use case we support very well, but it is
possible), referenced commits and trees are still fetched - only the
blobs are not fetched.

The necessary code change is done in fetch_pack() instead of somewhere
closer to where the "filter" instruction is written to the wire so that
only one part of the code needs to be changed in order for users of all
protocol versions to benefit from this optimization.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 fetch-pack.c             | 14 ++++++++++++++
 fetch-pack.h             |  7 +++++++
 t/t0410-partial-clone.sh | 41 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+)

diff --git a/fetch-pack.c b/fetch-pack.c
index b9b1211dda..5d82666a52 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1615,6 +1615,20 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 	if (nr_sought)
 		nr_sought = remove_duplicates_in_refs(sought, nr_sought);
 
+	if (args->no_dependents && !args->filter_options.choice) {
+		/*
+		 * The protocol does not support requesting that only the
+		 * wanted objects be sent, so approximate this by setting a
+		 * "blob:none" filter if no filter is already set. This works
+		 * for all object types: note that wanted blobs will still be
+		 * sent because they are directly specified as a "want".
+		 *
+		 * NEEDSWORK: Add an option in the protocol to request that
+		 * only the wanted objects be sent, and implement it.
+		 */
+		parse_list_objects_filter(&args->filter_options, "blob:none");
+	}
+
 	if (!ref) {
 		packet_flush(fd[1]);
 		die(_("no matching remote head"));
diff --git a/fetch-pack.h b/fetch-pack.h
index 5b6e868802..43ec344d95 100644
--- a/fetch-pack.h
+++ b/fetch-pack.h
@@ -43,6 +43,13 @@ struct fetch_pack_args {
 	unsigned from_promisor:1;
 
 	/*
+	 * Attempt to fetch only the wanted objects, and not any objects
+	 * referred to by them. Due to protocol limitations, extraneous
+	 * objects may still be included. (When fetching non-blob
+	 * objects, only blobs are excluded; when fetching a blob, the
+	 * blob itself will still be sent. The client does not need to
+	 * know whether a wanted object is a blob or not.)
+	 *
 	 * If 1, fetch_pack() will also not modify any object flags.
 	 * This allows fetch_pack() to safely be called by any function,
 	 * regardless of which object flags it uses (if any).
diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index cfd0655ea1..c521d7d6c6 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -182,6 +182,47 @@ test_expect_success 'fetching of missing objects works with ref-in-want enabled'
 	grep "git< fetch=.*ref-in-want" trace
 '
 
+test_expect_success 'fetching of missing blobs works' '
+	rm -rf server repo &&
+	test_create_repo server &&
+	test_commit -C server foo &&
+	git -C server repack -a -d --write-bitmap-index &&
+
+	git clone "file://$(pwd)/server" repo &&
+	git hash-object repo/foo.t >blobhash &&
+	rm -rf repo/.git/objects/* &&
+
+	git -C server config uploadpack.allowanysha1inwant 1 &&
+	git -C server config uploadpack.allowfilter 1 &&
+	git -C repo config core.repositoryformatversion 1 &&
+	git -C repo config extensions.partialclone "origin" &&
+
+	git -C repo cat-file -p $(cat blobhash)
+'
+
+test_expect_success 'fetching of missing trees does not fetch blobs' '
+	rm -rf server repo &&
+	test_create_repo server &&
+	test_commit -C server foo &&
+	git -C server repack -a -d --write-bitmap-index &&
+
+	git clone "file://$(pwd)/server" repo &&
+	git -C repo rev-parse foo^{tree} >treehash &&
+	git hash-object repo/foo.t >blobhash &&
+	rm -rf repo/.git/objects/* &&
+
+	git -C server config uploadpack.allowanysha1inwant 1 &&
+	git -C server config uploadpack.allowfilter 1 &&
+	git -C repo config core.repositoryformatversion 1 &&
+	git -C repo config extensions.partialclone "origin" &&
+	git -C repo cat-file -p $(cat treehash) &&
+
+	# Ensure that the tree, but not the blob, is fetched
+	git -C repo rev-list --objects --missing=print $(cat treehash) >objects &&
+	grep "^$(cat treehash)" objects &&
+	grep "^[?]$(cat blobhash)" objects
+'
+
 test_expect_success 'rev-list stops traversal at missing and promised commit' '
 	rm -rf repo &&
 	test_create_repo repo &&
-- 
2.19.0.605.g01d371f741-goog