From 738f8baafe7b0bc9d908b072c5a9b3d5347cff11 Mon Sep 17 00:00:00 2001
From: Justin Tobler <jltobler@gmail.com>
Date: Tue, 23 Jun 2026 23:19:15 -0500
Subject: [PATCH 1/6] object-file: rename files transaction prepare function

The "files" ODB transaction backend lazily creates a temporary object
directory when the first loose object is written to the transaction via
`prepare_loose_object_transaction()`. In a subsequent commit, the
temporary directory is used to also write packfiles to.

Rename the function to `odb_transaction_files_prepare()` accordingly.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 object-file.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/object-file.c b/object-file.c
index bce941874e..9f5e51eda4 100644
--- a/object-file.c
+++ b/object-file.c
@@ -499,7 +499,7 @@ struct odb_transaction_files {
 	struct transaction_packfile packfile;
 };
 
-static void prepare_loose_object_transaction(struct odb_transaction *base)
+static void odb_transaction_files_prepare(struct odb_transaction *base)
 {
 	struct odb_transaction_files *transaction =
 		container_of_or_null(base, struct odb_transaction_files, base);
@@ -760,7 +760,7 @@ int write_loose_object(struct odb_source_loose *loose,
 	static struct strbuf filename = STRBUF_INIT;
 
 	if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT))
-		prepare_loose_object_transaction(loose->base.odb->transaction);
+		odb_transaction_files_prepare(loose->base.odb->transaction);
 
 	odb_loose_path(loose, &filename, oid);
 
@@ -824,7 +824,7 @@ int odb_source_loose_write_stream(struct odb_source_loose *loose,
 	int hdrlen;
 
 	if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT))
-		prepare_loose_object_transaction(loose->base.odb->transaction);
+		odb_transaction_files_prepare(loose->base.odb->transaction);
 
 	/* Since oid is not determined, save tmp file to odb path. */
 	strbuf_addf(&filename, "%s/", loose->base.path);

From bd0ca589723b00b1764203897a19a359996593e6 Mon Sep 17 00:00:00 2001
From: Justin Tobler <jltobler@gmail.com>
Date: Tue, 23 Jun 2026 23:19:16 -0500
Subject: [PATCH 2/6] object-file: propagate files transaction errors

The "files" transaction backend may encounter errors related to managing
the temporary directory used to stage objects, but silently ignores
these errors. Instead return errors encountered in the
`odb_transaction_files_{prepare,begin,commit}()` interfaces to allow
callers to handle as needed.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 object-file.c      | 41 ++++++++++++++++++++++++++++-------------
 object-file.h      |  5 +++--
 odb/source-files.c |  6 +-----
 odb/transaction.h  |  2 +-
 4 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/object-file.c b/object-file.c
index 9f5e51eda4..e846c4469b 100644
--- a/object-file.c
+++ b/object-file.c
@@ -499,7 +499,7 @@ struct odb_transaction_files {
 	struct transaction_packfile packfile;
 };
 
-static void odb_transaction_files_prepare(struct odb_transaction *base)
+static int odb_transaction_files_prepare(struct odb_transaction *base)
 {
 	struct odb_transaction_files *transaction =
 		container_of_or_null(base, struct odb_transaction_files, base);
@@ -511,11 +511,15 @@ static void odb_transaction_files_prepare(struct odb_transaction *base)
 	 * added at the time they call odb_transaction_files_begin.
 	 */
 	if (!transaction || transaction->objdir)
-		return;
+		return 0;
 
 	transaction->objdir = tmp_objdir_create(base->source->odb->repo, "bulk-fsync");
-	if (transaction->objdir)
-		tmp_objdir_replace_primary_odb(transaction->objdir, 0);
+	if (!transaction->objdir)
+		return -1;
+
+	tmp_objdir_replace_primary_odb(transaction->objdir, 0);
+
+	return 0;
 }
 
 static void fsync_loose_object_transaction(struct odb_transaction *base,
@@ -542,13 +546,13 @@ static void fsync_loose_object_transaction(struct odb_transaction *base,
 /*
  * Cleanup after batch-mode fsync_object_files.
  */
-static void flush_loose_object_transaction(struct odb_transaction_files *transaction)
+static int flush_loose_object_transaction(struct odb_transaction_files *transaction)
 {
 	struct strbuf temp_path = STRBUF_INIT;
 	struct tempfile *temp;
 
 	if (!transaction->objdir)
-		return;
+		return 0;
 
 	/*
 	 * Issue a full hardware flush against a temporary file to ensure
@@ -570,8 +574,12 @@ static void flush_loose_object_transaction(struct odb_transaction_files *transac
 	 * Make the object files visible in the primary ODB after their data is
 	 * fully durable.
 	 */
-	tmp_objdir_migrate(transaction->objdir);
+	if (tmp_objdir_migrate(transaction->objdir))
+		return -1;
+
 	transaction->objdir = NULL;
+
+	return 0;
 }
 
 /* Finalize a file on disk, and close it. */
@@ -1668,27 +1676,34 @@ out:
 	return ret;
 }
 
-static void odb_transaction_files_commit(struct odb_transaction *base)
+static int odb_transaction_files_commit(struct odb_transaction *base)
 {
 	struct odb_transaction_files *transaction =
 		container_of(base, struct odb_transaction_files, base);
 
-	flush_loose_object_transaction(transaction);
+	if (flush_loose_object_transaction(transaction))
+		return -1;
 	flush_packfile_transaction(transaction);
+
+	return 0;
 }
 
-struct odb_transaction *odb_transaction_files_begin(struct odb_source *source)
+int odb_transaction_files_begin(struct odb_source *source,
+				struct odb_transaction **out)
 {
 	struct odb_transaction_files *transaction;
 	struct object_database *odb = source->odb;
 
-	if (odb->transaction)
-		return NULL;
+	if (odb->transaction) {
+		*out = NULL;
+		return 0;
+	}
 
 	transaction = xcalloc(1, sizeof(*transaction));
 	transaction->base.source = source;
 	transaction->base.commit = odb_transaction_files_commit;
 	transaction->base.write_object_stream = odb_transaction_files_write_object_stream;
+	*out = &transaction->base;
 
-	return &transaction->base;
+	return 0;
 }
diff --git a/object-file.h b/object-file.h
index 528c4e6e69..ac927fec07 100644
--- a/object-file.h
+++ b/object-file.h
@@ -195,8 +195,9 @@ struct odb_transaction;
  * Tell the object database to optimize for adding
  * multiple objects. odb_transaction_files_commit must be called
  * to make new objects visible. If a transaction is already
- * pending, NULL is returned.
+ * pending, out is set to NULL.
  */
-struct odb_transaction *odb_transaction_files_begin(struct odb_source *source);
+int odb_transaction_files_begin(struct odb_source *source,
+				struct odb_transaction **out);
 
 #endif /* OBJECT_FILE_H */
diff --git a/odb/source-files.c b/odb/source-files.c
index 5bdd042922..2545bd81d4 100644
--- a/odb/source-files.c
+++ b/odb/source-files.c
@@ -182,11 +182,7 @@ static int odb_source_files_write_object_stream(struct odb_source *source,
 static int odb_source_files_begin_transaction(struct odb_source *source,
 					      struct odb_transaction **out)
 {
-	struct odb_transaction *tx = odb_transaction_files_begin(source);
-	if (!tx)
-		return -1;
-	*out = tx;
-	return 0;
+	return odb_transaction_files_begin(source, out);
 }
 
 static int odb_source_files_read_alternates(struct odb_source *source,
diff --git a/odb/transaction.h b/odb/transaction.h
index 854fda06f5..f4c1ebfaaa 100644
--- a/odb/transaction.h
+++ b/odb/transaction.h
@@ -17,7 +17,7 @@ struct odb_transaction {
 	struct odb_source *source;
 
 	/* The ODB source specific callback invoked to commit a transaction. */
-	void (*commit)(struct odb_transaction *transaction);
+	int (*commit)(struct odb_transaction *transaction);
 
 	/*
 	 * This callback is expected to write the given object stream into

From 1bfc358fd8a686929329517b62a8534825facd3e Mon Sep 17 00:00:00 2001
From: Justin Tobler <jltobler@gmail.com>
Date: Tue, 23 Jun 2026 23:19:17 -0500
Subject: [PATCH 3/6] odb/transaction: propagate begin errors

When `odb_transaction_begin()` is invoked, the function returns the
transaction pointer directly. There is no way for the backend to
signal that it failed to set up its state, such as when creating the
temporary object directory backing the transaction.

In a subsequent commit, git-receive-pack(1) starts using ODB
transactions and needs to be able to report such failures rather
than silently ignore them. Refactor `odb_transaction_begin()` to
return an int error code and write the resulting transaction into an
out parameter. Also introduce `odb_transaction_begin_or_die()` as a
convenience for callsites that do not need to handle errors
explicitly.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/add.c            |  2 +-
 builtin/unpack-objects.c |  2 +-
 builtin/update-index.c   |  2 +-
 cache-tree.c             |  2 +-
 object-file.c            |  3 ++-
 odb/transaction.c        | 16 +++++++++++-----
 odb/transaction.h        | 19 +++++++++++++++----
 read-cache.c             |  2 +-
 8 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/builtin/add.c b/builtin/add.c
index c859f66519..3d5d9cfdb9 100644
--- a/builtin/add.c
+++ b/builtin/add.c
@@ -581,7 +581,7 @@ int cmd_add(int argc,
 		string_list_clear(&only_match_skip_worktree, 0);
 	}
 
-	transaction = odb_transaction_begin(repo->objects);
+	odb_transaction_begin_or_die(repo->objects, &transaction);
 
 	ps_matched = xcalloc(pathspec.nr, 1);
 	if (add_renormalize)
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index 59e9b8711e..1a195bf045 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -596,7 +596,7 @@ static void unpack_all(void)
 		progress = start_progress(the_repository,
 					  _("Unpacking objects"), nr_objects);
 	CALLOC_ARRAY(obj_list, nr_objects);
-	transaction = odb_transaction_begin(the_repository->objects);
+	odb_transaction_begin_or_die(the_repository->objects, &transaction);
 	for (i = 0; i < nr_objects; i++) {
 		unpack_one(i);
 		display_progress(progress, i + 1);
diff --git a/builtin/update-index.c b/builtin/update-index.c
index 3d6646c318..17f3ea284c 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -1124,7 +1124,7 @@ int cmd_update_index(int argc,
 	 * Allow the object layer to optimize adding multiple objects in
 	 * a batch.
 	 */
-	transaction = odb_transaction_begin(the_repository->objects);
+	odb_transaction_begin_or_die(the_repository->objects, &transaction);
 	while (ctx.argc) {
 		if (parseopt_state != PARSE_OPT_DONE)
 			parseopt_state = parse_options_step(&ctx, options,
diff --git a/cache-tree.c b/cache-tree.c
index 184f7e2635..1a7dfed9cf 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -490,7 +490,7 @@ int cache_tree_update(struct index_state *istate, int flags)
 
 	trace_performance_enter();
 	trace2_region_enter("cache_tree", "update", istate->repo);
-	transaction = odb_transaction_begin(the_repository->objects);
+	odb_transaction_begin_or_die(the_repository->objects, &transaction);
 	i = update_one(istate->cache_tree, istate->cache, istate->cache_nr,
 		       "", 0, &skip, flags);
 	odb_transaction_commit(transaction);
diff --git a/object-file.c b/object-file.c
index e846c4469b..85654b3fb9 100644
--- a/object-file.c
+++ b/object-file.c
@@ -1387,8 +1387,9 @@ int index_fd(struct index_state *istate, struct object_id *oid,
 
 		if (flags & INDEX_WRITE_OBJECT) {
 			struct object_database *odb = the_repository->objects;
-			struct odb_transaction *transaction = odb_transaction_begin(odb);
+			struct odb_transaction *transaction;
 
+			odb_transaction_begin_or_die(odb, &transaction);
 			ret = odb_transaction_write_object_stream(odb->transaction,
 								  &stream,
 								  xsize_t(st->st_size),
diff --git a/odb/transaction.c b/odb/transaction.c
index b16e07aebf..d3de01db50 100644
--- a/odb/transaction.c
+++ b/odb/transaction.c
@@ -2,14 +2,20 @@
 #include "odb/source.h"
 #include "odb/transaction.h"
 
-struct odb_transaction *odb_transaction_begin(struct object_database *odb)
+int odb_transaction_begin(struct object_database *odb,
+			  struct odb_transaction **out)
 {
-	if (odb->transaction)
-		return NULL;
+	int ret;
 
-	odb_source_begin_transaction(odb->sources, &odb->transaction);
+	if (odb->transaction) {
+		*out = NULL;
+		return 0;
+	}
 
-	return odb->transaction;
+	ret = odb_source_begin_transaction(odb->sources, out);
+	odb->transaction = *out;
+
+	return ret;
 }
 
 void odb_transaction_commit(struct odb_transaction *transaction)
diff --git a/odb/transaction.h b/odb/transaction.h
index f4c1ebfaaa..cd6d50f2e5 100644
--- a/odb/transaction.h
+++ b/odb/transaction.h
@@ -1,6 +1,8 @@
 #ifndef ODB_TRANSACTION_H
 #define ODB_TRANSACTION_H
 
+#include "git-compat-util.h"
+#include "gettext.h"
 #include "odb.h"
 #include "odb/source.h"
 
@@ -33,11 +35,20 @@ struct odb_transaction {
 };
 
 /*
- * Starts an ODB transaction. Subsequent objects are written to the transaction
- * and not committed until odb_transaction_commit() is invoked on the
- * transaction. If the ODB already has a pending transaction, NULL is returned.
+ * Starts an ODB transaction and returns it via `out`. Subsequent objects are
+ * written to the transaction and not committed until odb_transaction_commit()
+ * is invoked on the transaction. Returns 0 on success and a negative value on
+ * error. If the ODB already has a pending transaction, `out` is set to NULL.
  */
-struct odb_transaction *odb_transaction_begin(struct object_database *odb);
+int odb_transaction_begin(struct object_database *odb,
+			  struct odb_transaction **out);
+
+static inline void odb_transaction_begin_or_die(struct object_database *odb,
+						struct odb_transaction **out)
+{
+	if (odb_transaction_begin(odb, out))
+		die(_("failed to start ODB transaction"));
+}
 
 /*
  * Commits an ODB transaction making the written objects visible. If the
diff --git a/read-cache.c b/read-cache.c
index 21829102ae..3e629de340 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -4042,7 +4042,7 @@ int add_files_to_cache(struct repository *repo, const char *prefix,
 	 * This function is invoked from commands other than 'add', which
 	 * may not have their own transaction active.
 	 */
-	transaction = odb_transaction_begin(repo->objects);
+	odb_transaction_begin_or_die(repo->objects, &transaction);
 	run_diff_files(&rev, DIFF_RACY_IS_MODIFIED);
 	odb_transaction_commit(transaction);
 

From a72d74fa595c8bf1ecd843fc3c611ad6f8b4bbc5 Mon Sep 17 00:00:00 2001
From: Justin Tobler <jltobler@gmail.com>
Date: Tue, 23 Jun 2026 23:19:18 -0500
Subject: [PATCH 4/6] odb/transaction: propagate commit errors

When `odb_transaction_commit()` is invoked, the return value of the
backend commit callback is silently discarded. A backend has no way
to signal that committing failed, such as when the "files" backend
cannot migrate its temporary object directory into the permanent
ODB.

In a subsequent commit, git-receive-pack(1) starts using ODB transaction
to stage objects and consequently cares about such failures so it can
handle the error appropriately. Change the commit callback signature to
return an int error code and have `odb_transaction_commit()` forward it
accordingly.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 odb/transaction.c | 13 ++++++++++---
 odb/transaction.h |  2 +-
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/odb/transaction.c b/odb/transaction.c
index d3de01db50..b20d6a16f8 100644
--- a/odb/transaction.c
+++ b/odb/transaction.c
@@ -18,19 +18,26 @@ int odb_transaction_begin(struct object_database *odb,
 	return ret;
 }
 
-void odb_transaction_commit(struct odb_transaction *transaction)
+int odb_transaction_commit(struct odb_transaction *transaction)
 {
+	int ret;
+
 	if (!transaction)
-		return;
+		return 0;
 
 	/*
 	 * Ensure the transaction ending matches the pending transaction.
 	 */
 	ASSERT(transaction == transaction->source->odb->transaction);
 
-	transaction->commit(transaction);
+	ret = transaction->commit(transaction);
+	if (ret)
+		return ret;
+
 	transaction->source->odb->transaction = NULL;
 	free(transaction);
+
+	return 0;
 }
 
 int odb_transaction_write_object_stream(struct odb_transaction *transaction,
diff --git a/odb/transaction.h b/odb/transaction.h
index cd6d50f2e5..7898770071 100644
--- a/odb/transaction.h
+++ b/odb/transaction.h
@@ -54,7 +54,7 @@ static inline void odb_transaction_begin_or_die(struct object_database *odb,
  * Commits an ODB transaction making the written objects visible. If the
  * specified transaction is NULL, the function is a no-op.
  */
-void odb_transaction_commit(struct odb_transaction *transaction);
+int odb_transaction_commit(struct odb_transaction *transaction);
 
 /*
  * Writes the object in the provided stream into the transaction. The resulting

From ffab7256ac96a97aa275d2b92e5f9681eeae2820 Mon Sep 17 00:00:00 2001
From: Justin Tobler <jltobler@gmail.com>
Date: Tue, 23 Jun 2026 23:19:19 -0500
Subject: [PATCH 5/6] odb/transaction: add transaction env interface

The ODB transaction backend is responsible for creating/managing its own
staging area for writing objects. Other child processes spawned by Git
may need to access to uncommitted objects or write new objects in the
staging area though.

Introduce `odb_transaction_env()` which is expected to provide the set
of environment variables needed by a child process to access the
transaction staging area.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 object-file.c     | 11 +++++++++++
 odb/transaction.c |  8 ++++++++
 odb/transaction.h | 19 +++++++++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/object-file.c b/object-file.c
index 85654b3fb9..5172ff33ed 100644
--- a/object-file.c
+++ b/object-file.c
@@ -1689,6 +1689,16 @@ static int odb_transaction_files_commit(struct odb_transaction *base)
 	return 0;
 }
 
+static const char **odb_transaction_files_env(struct odb_transaction *base)
+{
+	struct odb_transaction_files *transaction =
+		container_of(base, struct odb_transaction_files, base);
+
+	odb_transaction_files_prepare(&transaction->base);
+
+	return tmp_objdir_env(transaction->objdir);
+}
+
 int odb_transaction_files_begin(struct odb_source *source,
 				struct odb_transaction **out)
 {
@@ -1704,6 +1714,7 @@ int odb_transaction_files_begin(struct odb_source *source,
 	transaction->base.source = source;
 	transaction->base.commit = odb_transaction_files_commit;
 	transaction->base.write_object_stream = odb_transaction_files_write_object_stream;
+	transaction->base.env = odb_transaction_files_env;
 	*out = &transaction->base;
 
 	return 0;
diff --git a/odb/transaction.c b/odb/transaction.c
index b20d6a16f8..20d3f43f54 100644
--- a/odb/transaction.c
+++ b/odb/transaction.c
@@ -46,3 +46,11 @@ int odb_transaction_write_object_stream(struct odb_transaction *transaction,
 {
 	return transaction->write_object_stream(transaction, stream, len, oid);
 }
+
+const char **odb_transaction_env(struct odb_transaction *transaction)
+{
+	if (!transaction)
+		return NULL;
+
+	return transaction->env(transaction);
+}
diff --git a/odb/transaction.h b/odb/transaction.h
index 7898770071..536458297b 100644
--- a/odb/transaction.h
+++ b/odb/transaction.h
@@ -32,6 +32,16 @@ struct odb_transaction {
 	int (*write_object_stream)(struct odb_transaction *transaction,
 				   struct odb_write_stream *stream, size_t len,
 				   struct object_id *oid);
+
+	/*
+	 * This callback is expected to return a NULL-terminated array of
+	 * environment variables that a child process should inherit so
+	 * that its object writes participate in the transaction. The
+	 * returned array is owned by the backend and remains valid until
+	 * the transaction ends. May return NULL when the backend does not
+	 * need to expose any state to child processes.
+	 */
+	const char **(*env)(struct odb_transaction *transaction);
 };
 
 /*
@@ -65,4 +75,13 @@ int odb_transaction_write_object_stream(struct odb_transaction *transaction,
 					struct odb_write_stream *stream,
 					size_t len, struct object_id *oid);
 
+/*
+ * Returns a NULL-terminated array of environment variables that a child
+ * process should inherit so that its object writes participate in the
+ * transaction, suitable for passing via child_process.env. Returns NULL if
+ * the transaction is NULL or the backend does not expose any state to child
+ * processes.
+ */
+const char **odb_transaction_env(struct odb_transaction *transaction);
+
 #endif

From fa7dbe2e4f8154ff0026382e4d47e4d176455407 Mon Sep 17 00:00:00 2001
From: Justin Tobler <jltobler@gmail.com>
Date: Tue, 23 Jun 2026 23:19:20 -0500
Subject: [PATCH 6/6] builtin/receive-pack: stage incoming objects via ODB
 transactions

Objects received by git-receive-pack(1) are quarantined in a temporary
"incoming" directory and migrated into the object database prior to the
reference updates. The quarantine is currently managed through
`tmp_objdir` directly. In a pluggable ODB future, how exactly an object
gets written to a transaction may vary for a given ODB source. Refactor
git-receive-pack(1) to use the ODB transaction interfaces to manage the
object staging area in a more agnostic manner accordingly.

Note that the temporary directory created for git-receive-pack(1) is
eagerly created and uses a different prefix name. This behavior is
special cased in the "files" backend by having `odb_transaction_begin()`
callers that require this behavior provide an `ODB_TRANSACTION_RECEIVE`
flag.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/add.c            |  2 +-
 builtin/receive-pack.c   | 46 ++++++++++++++++------------------------
 builtin/unpack-objects.c |  2 +-
 builtin/update-index.c   |  2 +-
 cache-tree.c             |  2 +-
 object-file.c            | 22 ++++++++++++++++---
 object-file.h            |  4 +++-
 odb/source-files.c       |  5 +++--
 odb/source-inmemory.c    |  3 ++-
 odb/source-loose.c       |  3 ++-
 odb/source.h             |  9 +++++---
 odb/transaction.c        |  5 +++--
 odb/transaction.h        | 13 ++++++++----
 read-cache.c             |  2 +-
 14 files changed, 70 insertions(+), 50 deletions(-)

diff --git a/builtin/add.c b/builtin/add.c
index 3d5d9cfdb9..60ffbede2b 100644
--- a/builtin/add.c
+++ b/builtin/add.c
@@ -581,7 +581,7 @@ int cmd_add(int argc,
 		string_list_clear(&only_match_skip_worktree, 0);
 	}
 
-	odb_transaction_begin_or_die(repo->objects, &transaction);
+	odb_transaction_begin_or_die(repo->objects, &transaction, 0);
 
 	ps_matched = xcalloc(pathspec.nr, 1);
 	if (add_renormalize)
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 19eb6a1b61..ee8e03e2ab 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -112,8 +112,6 @@ static enum {
 } use_keepalive;
 static int keepalive_in_sec = 5;
 
-static struct tmp_objdir *tmp_objdir;
-
 static struct proc_receive_ref {
 	unsigned int want_add:1,
 		     want_delete:1,
@@ -959,8 +957,8 @@ static int run_receive_hook(struct command *commands,
 		strvec_push(&opt.env, "GIT_PUSH_OPTION_COUNT");
 	}
 
-	if (tmp_objdir)
-		strvec_pushv(&opt.env, tmp_objdir_env(tmp_objdir));
+	if (the_repository->objects->transaction)
+		strvec_pushv(&opt.env, odb_transaction_env(the_repository->objects->transaction));
 
 	prepare_push_cert_sha1(&opt);
 
@@ -1363,7 +1361,7 @@ static int update_shallow_ref(struct command *cmd, struct shallow_info *si)
 		    !delayed_reachability_test(si, i))
 			oid_array_append(&extra, &si->shallow->oid[i]);
 
-	opt.env = tmp_objdir_env(tmp_objdir);
+	opt.env = odb_transaction_env(the_repository->objects->transaction);
 	setup_alternate_shallow(&shallow_lock, &opt.shallow_file, &extra);
 	if (check_connected(command_singleton_iterator, cmd, &opt)) {
 		rollback_shallow_file(the_repository, &shallow_lock);
@@ -1802,7 +1800,7 @@ static void set_connectivity_errors(struct command *commands,
 			/* to be checked in update_shallow_ref() */
 			continue;
 
-		opt.env = tmp_objdir_env(tmp_objdir);
+		opt.env = odb_transaction_env(the_repository->objects->transaction);
 		if (!check_connected(command_singleton_iterator, &singleton,
 				     &opt))
 			continue;
@@ -2057,7 +2055,7 @@ static void execute_commands(struct command *commands,
 		data.si = si;
 		opt.err_fd = err_fd;
 		opt.progress = err_fd && !quiet;
-		opt.env = tmp_objdir_env(tmp_objdir);
+		opt.env = odb_transaction_env(the_repository->objects->transaction);
 		opt.exclude_hidden_refs_section = "receive";
 
 		if (check_connected(iterate_receive_command_list, &data, &opt))
@@ -2106,14 +2104,13 @@ static void execute_commands(struct command *commands,
 	 * Now we'll start writing out refs, which means the objects need
 	 * to be in their final positions so that other processes can see them.
 	 */
-	if (tmp_objdir_migrate(tmp_objdir) < 0) {
+	if (odb_transaction_commit(the_repository->objects->transaction)) {
 		for (cmd = commands; cmd; cmd = cmd->next) {
 			if (!cmd->error_string)
 				cmd->error_string = "unable to migrate objects to permanent storage";
 		}
 		return;
 	}
-	tmp_objdir = NULL;
 
 	check_aliased_updates(commands);
 
@@ -2326,7 +2323,8 @@ static void push_header_arg(struct strvec *args, struct pack_header *hdr)
 		     ntohl(hdr->hdr_version), ntohl(hdr->hdr_entries));
 }
 
-static const char *unpack(int err_fd, struct shallow_info *si)
+static const char *unpack(int err_fd, struct shallow_info *si,
+			  struct odb_transaction *transaction)
 {
 	struct pack_header hdr;
 	const char *hdr_err;
@@ -2351,20 +2349,7 @@ static const char *unpack(int err_fd, struct shallow_info *si)
 		strvec_push(&child.args, alt_shallow_file);
 	}
 
-	tmp_objdir = tmp_objdir_create(the_repository, "incoming");
-	if (!tmp_objdir) {
-		if (err_fd > 0)
-			close(err_fd);
-		return "unable to create temporary object directory";
-	}
-	strvec_pushv(&child.env, tmp_objdir_env(tmp_objdir));
-
-	/*
-	 * Normally we just pass the tmp_objdir environment to the child
-	 * processes that do the heavy lifting, but we may need to see these
-	 * objects ourselves to set up shallow information.
-	 */
-	tmp_objdir_add_as_alternate(tmp_objdir);
+	strvec_pushv(&child.env, odb_transaction_env(transaction));
 
 	if (ntohl(hdr.hdr_entries) < unpack_limit) {
 		strvec_push(&child.args, "unpack-objects");
@@ -2431,13 +2416,14 @@ static const char *unpack(int err_fd, struct shallow_info *si)
 	return NULL;
 }
 
-static const char *unpack_with_sideband(struct shallow_info *si)
+static const char *unpack_with_sideband(struct shallow_info *si,
+					struct odb_transaction *transaction)
 {
 	struct async muxer;
 	const char *ret;
 
 	if (!use_sideband)
-		return unpack(0, si);
+		return unpack(0, si, transaction);
 
 	use_keepalive = KEEPALIVE_AFTER_NUL;
 	memset(&muxer, 0, sizeof(muxer));
@@ -2446,7 +2432,7 @@ static const char *unpack_with_sideband(struct shallow_info *si)
 	if (start_async(&muxer))
 		return NULL;
 
-	ret = unpack(muxer.in, si);
+	ret = unpack(muxer.in, si, transaction);
 
 	finish_async(&muxer);
 	return ret;
@@ -2623,6 +2609,7 @@ int cmd_receive_pack(int argc,
 	struct oid_array ref = OID_ARRAY_INIT;
 	struct shallow_info si;
 	struct packet_reader reader;
+	struct odb_transaction *transaction = NULL;
 
 	struct option options[] = {
 		OPT__QUIET(&quiet, N_("quiet")),
@@ -2707,7 +2694,10 @@ int cmd_receive_pack(int argc,
 		if (!si.nr_ours && !si.nr_theirs)
 			shallow_update = 0;
 		if (!delete_only(commands)) {
-			unpack_status = unpack_with_sideband(&si);
+			if (odb_transaction_begin(the_repository->objects, &transaction, ODB_TRANSACTION_RECEIVE))
+				unpack_status = "unable to start ODB transaction";
+			else
+				unpack_status = unpack_with_sideband(&si, transaction);
 			update_shallow_info(commands, &si, &ref);
 		}
 		use_keepalive = KEEPALIVE_ALWAYS;
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index 1a195bf045..39c44282e5 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -596,7 +596,7 @@ static void unpack_all(void)
 		progress = start_progress(the_repository,
 					  _("Unpacking objects"), nr_objects);
 	CALLOC_ARRAY(obj_list, nr_objects);
-	odb_transaction_begin_or_die(the_repository->objects, &transaction);
+	odb_transaction_begin_or_die(the_repository->objects, &transaction, 0);
 	for (i = 0; i < nr_objects; i++) {
 		unpack_one(i);
 		display_progress(progress, i + 1);
diff --git a/builtin/update-index.c b/builtin/update-index.c
index 17f3ea284c..bf6ea60ef4 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -1124,7 +1124,7 @@ int cmd_update_index(int argc,
 	 * Allow the object layer to optimize adding multiple objects in
 	 * a batch.
 	 */
-	odb_transaction_begin_or_die(the_repository->objects, &transaction);
+	odb_transaction_begin_or_die(the_repository->objects, &transaction, 0);
 	while (ctx.argc) {
 		if (parseopt_state != PARSE_OPT_DONE)
 			parseopt_state = parse_options_step(&ctx, options,
diff --git a/cache-tree.c b/cache-tree.c
index 1a7dfed9cf..ed05acc4c7 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -490,7 +490,7 @@ int cache_tree_update(struct index_state *istate, int flags)
 
 	trace_performance_enter();
 	trace2_region_enter("cache_tree", "update", istate->repo);
-	odb_transaction_begin_or_die(the_repository->objects, &transaction);
+	odb_transaction_begin_or_die(the_repository->objects, &transaction, 0);
 	i = update_one(istate->cache_tree, istate->cache, istate->cache_nr,
 		       "", 0, &skip, flags);
 	odb_transaction_commit(transaction);
diff --git a/object-file.c b/object-file.c
index 5172ff33ed..4a0e29e57c 100644
--- a/object-file.c
+++ b/object-file.c
@@ -497,6 +497,7 @@ struct odb_transaction_files {
 
 	struct tmp_objdir *objdir;
 	struct transaction_packfile packfile;
+	const char *prefix;
 };
 
 static int odb_transaction_files_prepare(struct odb_transaction *base)
@@ -513,7 +514,7 @@ static int odb_transaction_files_prepare(struct odb_transaction *base)
 	if (!transaction || transaction->objdir)
 		return 0;
 
-	transaction->objdir = tmp_objdir_create(base->source->odb->repo, "bulk-fsync");
+	transaction->objdir = tmp_objdir_create(base->source->odb->repo, transaction->prefix);
 	if (!transaction->objdir)
 		return -1;
 
@@ -1389,7 +1390,7 @@ int index_fd(struct index_state *istate, struct object_id *oid,
 			struct object_database *odb = the_repository->objects;
 			struct odb_transaction *transaction;
 
-			odb_transaction_begin_or_die(odb, &transaction);
+			odb_transaction_begin_or_die(odb, &transaction, 0);
 			ret = odb_transaction_write_object_stream(odb->transaction,
 								  &stream,
 								  xsize_t(st->st_size),
@@ -1700,7 +1701,8 @@ static const char **odb_transaction_files_env(struct odb_transaction *base)
 }
 
 int odb_transaction_files_begin(struct odb_source *source,
-				struct odb_transaction **out)
+				struct odb_transaction **out,
+				enum odb_transaction_flags flags)
 {
 	struct odb_transaction_files *transaction;
 	struct object_database *odb = source->odb;
@@ -1715,6 +1717,20 @@ int odb_transaction_files_begin(struct odb_source *source,
 	transaction->base.commit = odb_transaction_files_commit;
 	transaction->base.write_object_stream = odb_transaction_files_write_object_stream;
 	transaction->base.env = odb_transaction_files_env;
+
+	transaction->prefix = "bulk-fsync";
+	if (flags & ODB_TRANSACTION_RECEIVE) {
+		/*
+		 * ODB transactions for git-receive-pack(1) eagerly create a
+		 * temporary directory and use a different prefix.
+		 */
+		transaction->prefix = "incoming";
+		if (odb_transaction_files_prepare(&transaction->base)) {
+			free(transaction);
+			return -1;
+		}
+	}
+
 	*out = &transaction->base;
 
 	return 0;
diff --git a/object-file.h b/object-file.h
index ac927fec07..fe098d54cb 100644
--- a/object-file.h
+++ b/object-file.h
@@ -5,6 +5,7 @@
 #include "object.h"
 #include "odb.h"
 #include "odb/source-loose.h"
+#include "odb/transaction.h"
 
 /* The maximum size for an object header. */
 #define MAX_HEADER_LEN 32
@@ -198,6 +199,7 @@ struct odb_transaction;
  * pending, out is set to NULL.
  */
 int odb_transaction_files_begin(struct odb_source *source,
-				struct odb_transaction **out);
+				struct odb_transaction **out,
+				enum odb_transaction_flags flags);
 
 #endif /* OBJECT_FILE_H */
diff --git a/odb/source-files.c b/odb/source-files.c
index 2545bd81d4..534f48aad9 100644
--- a/odb/source-files.c
+++ b/odb/source-files.c
@@ -180,9 +180,10 @@ static int odb_source_files_write_object_stream(struct odb_source *source,
 }
 
 static int odb_source_files_begin_transaction(struct odb_source *source,
-					      struct odb_transaction **out)
+					      struct odb_transaction **out,
+					      enum odb_transaction_flags flags)
 {
-	return odb_transaction_files_begin(source, out);
+	return odb_transaction_files_begin(source, out, flags);
 }
 
 static int odb_source_files_read_alternates(struct odb_source *source,
diff --git a/odb/source-inmemory.c b/odb/source-inmemory.c
index e004566d76..9644d9d474 100644
--- a/odb/source-inmemory.c
+++ b/odb/source-inmemory.c
@@ -304,7 +304,8 @@ static int odb_source_inmemory_freshen_object(struct odb_source *source,
 }
 
 static int odb_source_inmemory_begin_transaction(struct odb_source *source UNUSED,
-						 struct odb_transaction **out UNUSED)
+						 struct odb_transaction **out UNUSED,
+						 enum odb_transaction_flags flags UNUSED)
 {
 	return error("in-memory source does not support transactions");
 }
diff --git a/odb/source-loose.c b/odb/source-loose.c
index 7d7ea2fb84..f4eac801e0 100644
--- a/odb/source-loose.c
+++ b/odb/source-loose.c
@@ -646,7 +646,8 @@ static int odb_source_loose_write_object_stream(struct odb_source *source,
 }
 
 static int odb_source_loose_begin_transaction(struct odb_source *source UNUSED,
-					      struct odb_transaction **out UNUSED)
+					      struct odb_transaction **out UNUSED,
+					      enum odb_transaction_flags flags UNUSED)
 {
 	/* TODO: this is a known omission that we'll want to address eventually. */
 	return error("loose source does not support transactions");
diff --git a/odb/source.h b/odb/source.h
index 8bcb67787e..c013762d33 100644
--- a/odb/source.h
+++ b/odb/source.h
@@ -3,6 +3,7 @@
 
 #include "object.h"
 #include "odb.h"
+#include "odb/transaction.h"
 
 enum odb_source_type {
 	/*
@@ -228,7 +229,8 @@ struct odb_source {
 	 * negative error code otherwise.
 	 */
 	int (*begin_transaction)(struct odb_source *source,
-				 struct odb_transaction **out);
+				 struct odb_transaction **out,
+				 enum odb_transaction_flags flags);
 
 	/*
 	 * This callback is expected to read the list of alternate object
@@ -467,9 +469,10 @@ static inline int odb_source_write_alternate(struct odb_source *source,
  * Returns 0 on success, a negative error code otherwise.
  */
 static inline int odb_source_begin_transaction(struct odb_source *source,
-					       struct odb_transaction **out)
+					       struct odb_transaction **out,
+					       enum odb_transaction_flags flags)
 {
-	return source->begin_transaction(source, out);
+	return source->begin_transaction(source, out, flags);
 }
 
 #endif
diff --git a/odb/transaction.c b/odb/transaction.c
index 20d3f43f54..34c212020c 100644
--- a/odb/transaction.c
+++ b/odb/transaction.c
@@ -3,7 +3,8 @@
 #include "odb/transaction.h"
 
 int odb_transaction_begin(struct object_database *odb,
-			  struct odb_transaction **out)
+			  struct odb_transaction **out,
+			  enum odb_transaction_flags flags)
 {
 	int ret;
 
@@ -12,7 +13,7 @@ int odb_transaction_begin(struct object_database *odb,
 		return 0;
 	}
 
-	ret = odb_source_begin_transaction(odb->sources, out);
+	ret = odb_source_begin_transaction(odb->sources, out, flags);
 	odb->transaction = *out;
 
 	return ret;
diff --git a/odb/transaction.h b/odb/transaction.h
index 536458297b..78392ff13d 100644
--- a/odb/transaction.h
+++ b/odb/transaction.h
@@ -4,7 +4,6 @@
 #include "git-compat-util.h"
 #include "gettext.h"
 #include "odb.h"
-#include "odb/source.h"
 
 /*
  * A transaction may be started for an object database prior to writing new
@@ -44,6 +43,10 @@ struct odb_transaction {
 	const char **(*env)(struct odb_transaction *transaction);
 };
 
+enum odb_transaction_flags {
+	ODB_TRANSACTION_RECEIVE = (1 << 0),
+};
+
 /*
  * Starts an ODB transaction and returns it via `out`. Subsequent objects are
  * written to the transaction and not committed until odb_transaction_commit()
@@ -51,12 +54,14 @@ struct odb_transaction {
  * error. If the ODB already has a pending transaction, `out` is set to NULL.
  */
 int odb_transaction_begin(struct object_database *odb,
-			  struct odb_transaction **out);
+			  struct odb_transaction **out,
+			  enum odb_transaction_flags flags);
 
 static inline void odb_transaction_begin_or_die(struct object_database *odb,
-						struct odb_transaction **out)
+						struct odb_transaction **out,
+						enum odb_transaction_flags flags)
 {
-	if (odb_transaction_begin(odb, out))
+	if (odb_transaction_begin(odb, out, flags))
 		die(_("failed to start ODB transaction"));
 }
 
diff --git a/read-cache.c b/read-cache.c
index 3e629de340..e7f508edb8 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -4042,7 +4042,7 @@ int add_files_to_cache(struct repository *repo, const char *prefix,
 	 * This function is invoked from commands other than 'add', which
 	 * may not have their own transaction active.
 	 */
-	odb_transaction_begin_or_die(repo->objects, &transaction);
+	odb_transaction_begin_or_die(repo->objects, &transaction, 0);
 	run_diff_files(&rev, DIFF_RACY_IS_MODIFIED);
 	odb_transaction_commit(transaction);