diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 5bdc44fb2de1fa2b0ee6f7adc49a6f63201c284d..c09cb342ee9cc9ba21ac9f13f420361a6846e7a1 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1716,7 +1716,7 @@ static int want_object_in_pack_mtime(const struct object_id *oid,
 		 */
 		struct odb_source *source = the_repository->objects->sources->next;
 		for (; source; source = source->next)
-			if (has_loose_object(source, oid))
+			if (odb_loose_source_has_object(source, oid))
 				return 0;
 	}
 
@@ -3980,7 +3980,7 @@ static void add_cruft_object_entry(const struct object_id *oid, enum object_type
 			int found = 0;
 
 			for (; !found && source; source = source->next)
-				if (has_loose_object(source, oid))
+				if (odb_loose_source_has_object(source, oid))
 					found = 1;
 
 			/*
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index ef79e43715d362d2907c23b5613d6fdaf9a96c80..d48f0dc488c743dc6b02ef9ada0c4f46c5a5a9b0 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -363,7 +363,7 @@ struct input_zstream_data {
 	int status;
 };
 
-static const void *feed_input_zstream(struct input_stream *in_stream,
+static const void *feed_input_zstream(struct odb_input_stream *in_stream,
 				      unsigned long *readlen)
 {
 	struct input_zstream_data *data = in_stream->data;
@@ -393,7 +393,7 @@ static void stream_blob(unsigned long size, unsigned nr)
 {
 	git_zstream zstream = { 0 };
 	struct input_zstream_data data = { 0 };
-	struct input_stream in_stream = {
+	struct odb_input_stream in_stream = {
 		.read = feed_input_zstream,
 		.data = &data,
 	};
@@ -402,8 +402,7 @@ static void stream_blob(unsigned long size, unsigned nr)
 	data.zstream = &zstream;
 	git_inflate_init(&zstream);
 
-	if (stream_loose_object(the_repository->objects->sources,
-				&in_stream, size, &info->oid))
+	if (odb_write_object_stream(the_repository->objects, &in_stream, size, &info->oid))
 		die(_("failed to write object in stream"));
 
 	if (data.status != Z_STREAM_END)
diff --git a/loose.c b/loose.c
index e8ea6e7e24ba31218579c92fb506b012f2b72f12..56cf64b648bf80c3d7d8e0649f87687138018743 100644
--- a/loose.c
+++ b/loose.c
@@ -1,6 +1,7 @@
 #include "git-compat-util.h"
 #include "hash.h"
 #include "path.h"
+#include "object-file.h"
 #include "odb.h"
 #include "hex.h"
 #include "repository.h"
@@ -48,13 +49,13 @@ static int insert_loose_map(struct odb_source *source,
 			    const struct object_id *oid,
 			    const struct object_id *compat_oid)
 {
-	struct loose_object_map *map = source->loose_map;
+	struct loose_object_map *map = source->loose->map;
 	int inserted = 0;
 
 	inserted |= insert_oid_pair(map->to_compat, oid, compat_oid);
 	inserted |= insert_oid_pair(map->to_storage, compat_oid, oid);
 	if (inserted)
-		oidtree_insert(source->loose_objects_cache, compat_oid);
+		oidtree_insert(source->loose->cache, compat_oid);
 
 	return inserted;
 }
@@ -64,11 +65,11 @@ static int load_one_loose_object_map(struct repository *repo, struct odb_source
 	struct strbuf buf = STRBUF_INIT, path = STRBUF_INIT;
 	FILE *fp;
 
-	if (!source->loose_map)
-		loose_object_map_init(&source->loose_map);
-	if (!source->loose_objects_cache) {
-		ALLOC_ARRAY(source->loose_objects_cache, 1);
-		oidtree_init(source->loose_objects_cache);
+	if (!source->loose->map)
+		loose_object_map_init(&source->loose->map);
+	if (!source->loose->cache) {
+		ALLOC_ARRAY(source->loose->cache, 1);
+		oidtree_init(source->loose->cache);
 	}
 
 	insert_loose_map(source, repo->hash_algo->empty_tree, repo->compat_hash_algo->empty_tree);
@@ -124,7 +125,7 @@ int repo_read_loose_object_map(struct repository *repo)
 
 int repo_write_loose_object_map(struct repository *repo)
 {
-	kh_oid_map_t *map = repo->objects->sources->loose_map->to_compat;
+	kh_oid_map_t *map = repo->objects->sources->loose->map->to_compat;
 	struct lock_file lock;
 	int fd;
 	khiter_t iter;
@@ -230,7 +231,7 @@ int repo_loose_object_map_oid(struct repository *repo,
 	khiter_t pos;
 
 	for (source = repo->objects->sources; source; source = source->next) {
-		struct loose_object_map *loose_map = source->loose_map;
+		struct loose_object_map *loose_map = source->loose->map;
 		if (!loose_map)
 			continue;
 		map = (to == repo->compat_hash_algo) ?
diff --git a/object-file.c b/object-file.c
index 4675c8ed6b67eb8b1f054aa7326f380d9a0a29b5..9f9cab6ffabf0283c797feb1872db6a01738e2ca 100644
--- a/object-file.c
+++ b/object-file.c
@@ -99,8 +99,8 @@ static int check_and_freshen_source(struct odb_source *source,
 	return check_and_freshen_file(path.buf, freshen);
 }
 
-int has_loose_object(struct odb_source *source,
-		     const struct object_id *oid)
+int odb_loose_source_has_object(struct odb_source *source,
+				const struct object_id *oid)
 {
 	return check_and_freshen_source(source, oid, 0);
 }
@@ -167,25 +167,22 @@ int stream_object_signature(struct repository *r, const struct object_id *oid)
 }
 
 /*
- * Find "oid" as a loose object in the local repository or in an alternate.
+ * Find "oid" as a loose object in given source.
  * Returns 0 on success, negative on failure.
  *
  * The "path" out-parameter will give the path of the object we found (if any).
  * Note that it may point to static storage and is only valid until another
  * call to stat_loose_object().
  */
-static int stat_loose_object(struct repository *r, const struct object_id *oid,
+static int stat_loose_object(struct odb_loose_source *source,
+			     const struct object_id *oid,
 			     struct stat *st, const char **path)
 {
-	struct odb_source *source;
 	static struct strbuf buf = STRBUF_INIT;
 
-	odb_prepare_alternates(r->objects);
-	for (source = r->objects->sources; source; source = source->next) {
-		*path = odb_loose_path(source, &buf, oid);
-		if (!lstat(*path, st))
-			return 0;
-	}
+	*path = odb_loose_path(source->source, &buf, oid);
+	if (!lstat(*path, st))
+		return 0;
 
 	return -1;
 }
@@ -194,39 +191,24 @@ static int stat_loose_object(struct repository *r, const struct object_id *oid,
  * Like stat_loose_object(), but actually open the object and return the
  * descriptor. See the caveats on the "path" parameter above.
  */
-static int open_loose_object(struct repository *r,
+static int open_loose_object(struct odb_loose_source *source,
 			     const struct object_id *oid, const char **path)
 {
-	int fd;
-	struct odb_source *source;
-	int most_interesting_errno = ENOENT;
 	static struct strbuf buf = STRBUF_INIT;
+	int fd;
 
-	odb_prepare_alternates(r->objects);
-	for (source = r->objects->sources; source; source = source->next) {
-		*path = odb_loose_path(source, &buf, oid);
-		fd = git_open(*path);
-		if (fd >= 0)
-			return fd;
+	*path = odb_loose_path(source->source, &buf, oid);
+	fd = git_open(*path);
+	if (fd >= 0)
+		return fd;
 
-		if (most_interesting_errno == ENOENT)
-			most_interesting_errno = errno;
-	}
-	errno = most_interesting_errno;
 	return -1;
 }
 
-static int quick_has_loose(struct repository *r,
+static int quick_has_loose(struct odb_loose_source *source,
 			   const struct object_id *oid)
 {
-	struct odb_source *source;
-
-	odb_prepare_alternates(r->objects);
-	for (source = r->objects->sources; source; source = source->next) {
-		if (oidtree_contains(odb_loose_cache(source, oid), oid))
-			return 1;
-	}
-	return 0;
+	return !!oidtree_contains(odb_loose_source_cache(source->source, oid), oid);
 }
 
 /*
@@ -252,12 +234,12 @@ static void *map_fd(int fd, const char *path, unsigned long *size)
 	return map;
 }
 
-void *map_loose_object(struct repository *r,
-		       const struct object_id *oid,
-		       unsigned long *size)
+void *odb_loose_source_map_object(struct odb_source *source,
+				  const struct object_id *oid,
+				  unsigned long *size)
 {
 	const char *p;
-	int fd = open_loose_object(r, oid, &p);
+	int fd = open_loose_object(source->loose, oid, &p);
 
 	if (fd < 0)
 		return NULL;
@@ -407,9 +389,9 @@ int parse_loose_header(const char *hdr, struct object_info *oi)
 	return 0;
 }
 
-int loose_object_info(struct repository *r,
-		      const struct object_id *oid,
-		      struct object_info *oi, int flags)
+int odb_loose_source_read_object_info(struct odb_source *source,
+				      const struct object_id *oid,
+				      struct object_info *oi, int flags)
 {
 	int status = 0;
 	int fd;
@@ -422,7 +404,7 @@ int loose_object_info(struct repository *r,
 	enum object_type type_scratch;
 
 	if (oi->delta_base_oid)
-		oidclr(oi->delta_base_oid, r->hash_algo);
+		oidclr(oi->delta_base_oid, source->odb->repo->hash_algo);
 
 	/*
 	 * If we don't care about type or size, then we don't
@@ -435,15 +417,15 @@ int loose_object_info(struct repository *r,
 	if (!oi->typep && !oi->sizep && !oi->contentp) {
 		struct stat st;
 		if (!oi->disk_sizep && (flags & OBJECT_INFO_QUICK))
-			return quick_has_loose(r, oid) ? 0 : -1;
-		if (stat_loose_object(r, oid, &st, &path) < 0)
+			return quick_has_loose(source->loose, oid) ? 0 : -1;
+		if (stat_loose_object(source->loose, oid, &st, &path) < 0)
 			return -1;
 		if (oi->disk_sizep)
 			*oi->disk_sizep = st.st_size;
 		return 0;
 	}
 
-	fd = open_loose_object(r, oid, &path);
+	fd = open_loose_object(source->loose, oid, &path);
 	if (fd < 0) {
 		if (errno != ENOENT)
 			error_errno(_("unable to open loose object %s"), oid_to_hex(oid));
@@ -986,35 +968,15 @@ static int write_loose_object(struct odb_source *source,
 					  FOF_SKIP_COLLISION_CHECK);
 }
 
-static int freshen_loose_object(struct object_database *odb,
-				const struct object_id *oid)
+int odb_loose_source_freshen_object(struct odb_source *source,
+				    const struct object_id *oid)
 {
-	odb_prepare_alternates(odb);
-	for (struct odb_source *source = odb->sources; source; source = source->next)
-		if (check_and_freshen_source(source, oid, 1))
-			return 1;
-	return 0;
+	return !!check_and_freshen_source(source, oid, 1);
 }
 
-static int freshen_packed_object(struct object_database *odb,
-				 const struct object_id *oid)
-{
-	struct pack_entry e;
-	if (!find_pack_entry(odb->repo, oid, &e))
-		return 0;
-	if (e.p->is_cruft)
-		return 0;
-	if (e.p->freshened)
-		return 1;
-	if (!freshen_file(e.p->pack_name))
-		return 0;
-	e.p->freshened = 1;
-	return 1;
-}
-
-int stream_loose_object(struct odb_source *source,
-			struct input_stream *in_stream, size_t len,
-			struct object_id *oid)
+int odb_loose_source_write_stream(struct odb_source *source,
+				  struct odb_input_stream *in_stream, size_t len,
+				  struct object_id *oid)
 {
 	const struct git_hash_algo *compat = source->odb->repo->compat_hash_algo;
 	struct object_id compat_oid;
@@ -1091,12 +1053,10 @@ int stream_loose_object(struct odb_source *source,
 		die(_("deflateEnd on stream object failed (%d)"), ret);
 	close_loose_object(source, fd, tmp_file.buf);
 
-	if (freshen_packed_object(source->odb, oid) ||
-	    freshen_loose_object(source->odb, oid)) {
+	if (odb_freshen_object(source->odb, oid)) {
 		unlink_or_warn(tmp_file.buf);
 		goto cleanup;
 	}
-
 	odb_loose_path(source, &filename, oid);
 
 	/* We finally know the object path, and create the missing dir. */
@@ -1124,10 +1084,10 @@ int stream_loose_object(struct odb_source *source,
 	return err;
 }
 
-int write_object_file(struct odb_source *source,
-		      const void *buf, unsigned long len,
-		      enum object_type type, struct object_id *oid,
-		      struct object_id *compat_oid_in, unsigned flags)
+int odb_loose_source_write_object(struct odb_source *source,
+				  const void *buf, unsigned long len,
+				  enum object_type type, struct object_id *oid,
+				  struct object_id *compat_oid_in, unsigned flags)
 {
 	const struct git_hash_algo *algo = source->odb->repo->hash_algo;
 	const struct git_hash_algo *compat = source->odb->repo->compat_hash_algo;
@@ -1155,8 +1115,7 @@ int write_object_file(struct odb_source *source,
 	 * it out into .git/objects/??/?{38} file.
 	 */
 	write_object_file_prepare(algo, buf, len, type, oid, hdr, &hdrlen);
-	if (freshen_packed_object(source->odb, oid) ||
-	    freshen_loose_object(source->odb, oid))
+	if (odb_freshen_object(source->odb, oid))
 		return 0;
 	if (write_loose_object(source, oid, hdr, hdrlen, buf, len, 0, flags))
 		return -1;
@@ -1179,7 +1138,7 @@ int force_object_loose(struct odb_source *source,
 	int ret;
 
 	for (struct odb_source *s = source->odb->sources; s; s = s->next)
-		if (has_loose_object(s, oid))
+		if (odb_loose_source_has_object(s, oid))
 			return 0;
 
 	oi.typep = &type;
@@ -1802,44 +1761,49 @@ static int append_loose_object(const struct object_id *oid,
 	return 0;
 }
 
-struct oidtree *odb_loose_cache(struct odb_source *source,
-				const struct object_id *oid)
+struct oidtree *odb_loose_source_cache(struct odb_source *source,
+				       const struct object_id *oid)
 {
 	int subdir_nr = oid->hash[0];
 	struct strbuf buf = STRBUF_INIT;
-	size_t word_bits = bitsizeof(source->loose_objects_subdir_seen[0]);
+	size_t word_bits = bitsizeof(source->loose->subdir_seen[0]);
 	size_t word_index = subdir_nr / word_bits;
 	size_t mask = (size_t)1u << (subdir_nr % word_bits);
 	uint32_t *bitmap;
 
 	if (subdir_nr < 0 ||
-	    (size_t) subdir_nr >= bitsizeof(source->loose_objects_subdir_seen))
+	    (size_t) subdir_nr >= bitsizeof(source->loose->subdir_seen))
 		BUG("subdir_nr out of range");
 
-	bitmap = &source->loose_objects_subdir_seen[word_index];
+	bitmap = &source->loose->subdir_seen[word_index];
 	if (*bitmap & mask)
-		return source->loose_objects_cache;
-	if (!source->loose_objects_cache) {
-		ALLOC_ARRAY(source->loose_objects_cache, 1);
-		oidtree_init(source->loose_objects_cache);
+		return source->loose->cache;
+	if (!source->loose->cache) {
+		ALLOC_ARRAY(source->loose->cache, 1);
+		oidtree_init(source->loose->cache);
 	}
 	strbuf_addstr(&buf, source->path);
 	for_each_file_in_obj_subdir(subdir_nr, &buf,
 				    source->odb->repo->hash_algo,
 				    append_loose_object,
 				    NULL, NULL,
-				    source->loose_objects_cache);
+				    source->loose->cache);
 	*bitmap |= mask;
 	strbuf_release(&buf);
-	return source->loose_objects_cache;
+	return source->loose->cache;
 }
 
-void odb_clear_loose_cache(struct odb_source *source)
+static void odb_loose_source_clear_cache(struct odb_loose_source *source)
 {
-	oidtree_clear(source->loose_objects_cache);
-	FREE_AND_NULL(source->loose_objects_cache);
-	memset(&source->loose_objects_subdir_seen, 0,
-	       sizeof(source->loose_objects_subdir_seen));
+	oidtree_clear(source->cache);
+	FREE_AND_NULL(source->cache);
+	memset(&source->subdir_seen, 0,
+	       sizeof(source->subdir_seen));
+}
+
+void odb_loose_source_reprepare(struct odb_source *source)
+{
+	odb_loose_source_clear_cache(source->loose);
 }
 
 static int check_stream_oid(git_zstream *stream,
@@ -1995,3 +1959,20 @@ void object_file_transaction_commit(struct odb_transaction *transaction)
 	transaction->odb->transaction = NULL;
 	free(transaction);
 }
+
+struct odb_loose_source *odb_loose_source_new(struct odb_source *source)
+{
+	struct odb_loose_source *loose;
+	CALLOC_ARRAY(loose, 1);
+	loose->source = source;
+	return loose;
+}
+
+void odb_loose_source_free(struct odb_loose_source *source)
+{
+	if (!source)
+		return;
+	odb_loose_source_clear_cache(source);
+	loose_object_map_clear(&source->map);
+	free(source);
+}
diff --git a/object-file.h b/object-file.h
index 3fd48dcafbf1dc797efabd489e68720e521a38d2..065811790bd4c170895a26c9138a1b39d30f5184 100644
--- a/object-file.h
+++ b/object-file.h
@@ -7,14 +7,6 @@
 
 struct index_state;
 
-/*
- * Set this to 0 to prevent odb_read_object_info_extended() from fetching missing
- * blobs. This has a difference only if extensions.partialClone is set.
- *
- * Its default value is 1.
- */
-extern int fetch_if_missing;
-
 enum {
 	INDEX_WRITE_OBJECT = (1 << 0),
 	INDEX_FORMAT_CHECK = (1 << 1),
@@ -26,15 +18,65 @@ int index_path(struct index_state *istate, struct object_id *oid, const char *pa
 
 struct odb_source;
 
+struct odb_loose_source {
+	struct odb_source *source;
+
+	/*
+	 * Used to store the results of readdir(3) calls when we are OK
+	 * sacrificing accuracy due to races for speed. That includes
+	 * object existence with OBJECT_INFO_QUICK, as well as
+	 * our search for unique abbreviated hashes. Don't use it for tasks
+	 * requiring greater accuracy!
+	 *
+	 * Be sure to call odb_load_loose_cache() before using.
+	 */
+	uint32_t subdir_seen[8]; /* 256 bits */
+	struct oidtree *cache;
+
+	/* Map between object IDs for loose objects. */
+	struct loose_object_map *map;
+};
+
+struct odb_loose_source *odb_loose_source_new(struct odb_source *source);
+void odb_loose_source_free(struct odb_loose_source *source);
+
+/* Reprepare the loose source by emptying the loose object cache. */
+void odb_loose_source_reprepare(struct odb_source *source);
+
+int odb_loose_source_read_object_info(struct odb_source *source,
+				      const struct object_id *oid,
+				      struct object_info *oi, int flags);
+
+void *odb_loose_source_map_object(struct odb_source *source,
+				  const struct object_id *oid,
+				  unsigned long *size);
+
 /*
- * Populate and return the loose object cache array corresponding to the
- * given object ID.
+ * Return true iff an object database source has a loose object
+ * with the specified name.  This function does not respect replace
+ * references.
  */
-struct oidtree *odb_loose_cache(struct odb_source *source,
+int odb_loose_source_has_object(struct odb_source *source,
 				const struct object_id *oid);
 
-/* Empty the loose object cache for the specified object directory. */
-void odb_clear_loose_cache(struct odb_source *source);
+int odb_loose_source_freshen_object(struct odb_source *source,
+				    const struct object_id *oid);
+
+int odb_loose_source_write_object(struct odb_source *source,
+				  const void *buf, unsigned long len,
+				  enum object_type type, struct object_id *oid,
+				  struct object_id *compat_oid_in, unsigned flags);
+
+int odb_loose_source_write_stream(struct odb_source *source,
+				  struct odb_input_stream *stream, size_t len,
+				  struct object_id *oid);
+
+/*
+ * Populate and return the loose object cache array corresponding to the
+ * given object ID.
+ */
+struct oidtree *odb_loose_source_cache(struct odb_source *source,
+				       const struct object_id *oid);
 
 /*
  * Put in `buf` the name of the file in the local object database that
@@ -44,17 +86,6 @@ const char *odb_loose_path(struct odb_source *source,
 			   struct strbuf *buf,
 			   const struct object_id *oid);
 
-/*
- * Return true iff an object database source has a loose object
- * with the specified name.  This function does not respect replace
- * references.
- */
-int has_loose_object(struct odb_source *source,
-		     const struct object_id *oid);
-
-void *map_loose_object(struct repository *r, const struct object_id *oid,
-		       unsigned long *size);
-
 /*
  * Iterate over the files in the loose-object parts of the object
  * directory "path", triggering the following callbacks:
@@ -146,21 +177,6 @@ enum unpack_loose_header_result unpack_loose_header(git_zstream *stream,
 struct object_info;
 int parse_loose_header(const char *hdr, struct object_info *oi);
 
-int write_object_file(struct odb_source *source,
-		      const void *buf, unsigned long len,
-		      enum object_type type, struct object_id *oid,
-		      struct object_id *compat_oid_in, unsigned flags);
-
-struct input_stream {
-	const void *(*read)(struct input_stream *, unsigned long *len);
-	void *data;
-	int is_finished;
-};
-
-int stream_loose_object(struct odb_source *source,
-			struct input_stream *in_stream, size_t len,
-			struct object_id *oid);
-
 int force_object_loose(struct odb_source *source,
 		       const struct object_id *oid, time_t mtime);
 
@@ -182,10 +198,6 @@ int check_object_signature(struct repository *r, const struct object_id *oid,
  */
 int stream_object_signature(struct repository *r, const struct object_id *oid);
 
-int loose_object_info(struct repository *r,
-		      const struct object_id *oid,
-		      struct object_info *oi, int flags);
-
 enum finalize_object_file_flags {
 	FOF_SKIP_COLLISION_CHECK = 1,
 };
diff --git a/object-name.c b/object-name.c
index f6902e140dd43eb7bd878306be4cfb26b050fbfe..77e33e693aa74d1d184cad2a5b3172085c76669d 100644
--- a/object-name.c
+++ b/object-name.c
@@ -116,7 +116,7 @@ static void find_short_object_filename(struct disambiguate_state *ds)
 	struct odb_source *source;
 
 	for (source = ds->repo->objects->sources; source && !ds->ambiguous; source = source->next)
-		oidtree_each(odb_loose_cache(source, &ds->bin_pfx),
+		oidtree_each(odb_loose_source_cache(source, &ds->bin_pfx),
 				&ds->bin_pfx, ds->len, match_prefix, ds);
 }
 
diff --git a/odb.c b/odb.c
index 00a6e71568b5985c0b344bfebbe92d1e0bff1294..cca07a5cc685f59edaca6ec3d3daa77342065dc8 100644
--- a/odb.c
+++ b/odb.c
@@ -86,17 +86,16 @@ int odb_mkstemp(struct object_database *odb,
 /*
  * Return non-zero iff the path is usable as an alternate object database.
  */
-static int alt_odb_usable(struct object_database *o,
-			  struct strbuf *path,
-			  const char *normalized_objdir, khiter_t *pos)
+static int alt_odb_usable(struct object_database *o, const char *path,
+			  const char *normalized_objdir)
 {
 	int r;
 
 	/* Detect cases where alternate disappeared */
-	if (!is_directory(path->buf)) {
+	if (!is_directory(path)) {
 		error(_("object directory %s does not exist; "
 			"check .git/objects/info/alternates"),
-		      path->buf);
+		      path);
 		return 0;
 	}
 
@@ -113,11 +112,14 @@ static int alt_odb_usable(struct object_database *o,
 		assert(r == 1); /* never used */
 		kh_value(o->source_by_path, p) = o->sources;
 	}
-	if (fspatheq(path->buf, normalized_objdir))
+
+	if (fspatheq(path, normalized_objdir))
+		return 0;
+
+	if (kh_get_odb_path_map(o->source_by_path, path) < kh_end(o->source_by_path))
 		return 0;
-	*pos = kh_put_odb_path_map(o->source_by_path, path->buf, &r);
-	/* r: 0 = exists, 1 = never used, 2 = deleted */
-	return r == 0 ? 0 : 1;
+
+	return 1;
 }
 
 /*
@@ -139,6 +141,21 @@ static void read_info_alternates(struct object_database *odb,
 				 const char *relative_base,
 				 int depth);
 
+struct odb_source *odb_source_new(struct object_database *odb,
+				  const char *path,
+				  bool local)
+{
+	struct odb_source *source;
+
+	CALLOC_ARRAY(source, 1);
+	source->odb = odb;
+	source->local = local;
+	source->path = xstrdup(path);
+	source->loose = odb_loose_source_new(source);
+
+	return source;
+}
+
 static struct odb_source *link_alt_odb_entry(struct object_database *odb,
 					     const char *dir,
 					     const char *relative_base,
@@ -148,6 +165,7 @@ static struct odb_source *link_alt_odb_entry(struct object_database *odb,
 	struct strbuf pathbuf = STRBUF_INIT;
 	struct strbuf tmp = STRBUF_INIT;
 	khiter_t pos;
+	int ret;
 
 	if (!is_absolute_path(dir) && relative_base) {
 		strbuf_realpath(&pathbuf, relative_base, 1);
@@ -172,20 +190,18 @@ static struct odb_source *link_alt_odb_entry(struct object_database *odb,
 	strbuf_reset(&tmp);
 	strbuf_realpath(&tmp, odb->sources->path, 1);
 
-	if (!alt_odb_usable(odb, &pathbuf, tmp.buf, &pos))
+	if (!alt_odb_usable(odb, pathbuf.buf, tmp.buf))
 		goto error;
 
-	CALLOC_ARRAY(alternate, 1);
-	alternate->odb = odb;
-	alternate->local = false;
-	/* pathbuf.buf is already in r->objects->source_by_path */
-	alternate->path = strbuf_detach(&pathbuf, NULL);
+	alternate = odb_source_new(odb, pathbuf.buf, false);
 
 	/* add the alternate entry */
 	*odb->sources_tail = alternate;
 	odb->sources_tail = &(alternate->next);
-	alternate->next = NULL;
-	assert(odb->source_by_path);
+
+	pos = kh_put_odb_path_map(odb->source_by_path, alternate->path, &ret);
+	if (!ret)
+		BUG("source must not yet exist");
 	kh_value(odb->source_by_path, pos) = alternate;
 
 	/* recursively add alternates */
@@ -337,9 +353,7 @@ struct odb_source *odb_set_temporary_primary_source(struct object_database *odb,
 	 * Make a new primary odb and link the old primary ODB in as an
 	 * alternate
 	 */
-	source = xcalloc(1, sizeof(*source));
-	source->odb = odb;
-	source->path = xstrdup(dir);
+	source = odb_source_new(odb, dir, false);
 
 	/*
 	 * Disable ref updates while a temporary odb is active, since
@@ -352,11 +366,10 @@ struct odb_source *odb_set_temporary_primary_source(struct object_database *odb,
 	return source->next;
 }
 
-static void free_object_directory(struct odb_source *source)
+static void odb_source_free(struct odb_source *source)
 {
 	free(source->path);
-	odb_clear_loose_cache(source);
-	loose_object_map_clear(&source->loose_map);
+	odb_loose_source_free(source->loose);
 	free(source);
 }
 
@@ -374,7 +387,7 @@ void odb_restore_primary_source(struct object_database *odb,
 		BUG("we expect the old primary object store to be the first alternate");
 
 	odb->sources = restore_source;
-	free_object_directory(cur_source);
+	odb_source_free(cur_source);
 }
 
 char *compute_alternate_path(const char *path, struct strbuf *err)
@@ -684,13 +697,18 @@ static int do_oid_object_info_extended(struct object_database *odb,
 		return 0;
 	}
 
+	odb_prepare_alternates(odb);
+
 	while (1) {
+		struct odb_source *source;
+
 		if (find_pack_entry(odb->repo, real, &e))
 			break;
 
 		/* Most likely it's a loose object. */
-		if (!loose_object_info(odb->repo, real, oi, flags))
-			return 0;
+		for (source = odb->sources; source; source = source->next)
+			if (!odb_loose_source_read_object_info(source, real, oi, flags))
+				return 0;
 
 		/* Not a loose object; someone else may have just packed it. */
 		if (!(flags & OBJECT_INFO_QUICK)) {
@@ -969,6 +987,22 @@ int odb_has_object(struct object_database *odb, const struct object_id *oid,
 	return odb_read_object_info_extended(odb, oid, NULL, object_info_flags) >= 0;
 }
 
+int odb_freshen_object(struct object_database *odb,
+		       const struct object_id *oid)
+{
+	struct odb_source *source;
+
+	if (packfile_store_freshen_object(odb->packfiles, oid))
+		return 1;
+
+	odb_prepare_alternates(odb);
+	for (source = odb->sources; source; source = source->next)
+		if (odb_loose_source_freshen_object(source, oid))
+			return 1;
+
+	return 0;
+}
+
 void odb_assert_oid_type(struct object_database *odb,
 			 const struct object_id *oid, enum object_type expect)
 {
@@ -987,7 +1021,15 @@ int odb_write_object_ext(struct object_database *odb,
 			 struct object_id *compat_oid,
 			 unsigned flags)
 {
-	return write_object_file(odb->sources, buf, len, type, oid, compat_oid, flags);
+	return odb_loose_source_write_object(odb->sources, buf, len, type,
+					     oid, compat_oid, flags);
+}
+
+int odb_write_object_stream(struct object_database *odb,
+			    struct odb_input_stream *stream, size_t len,
+			    struct object_id *oid)
+{
+	return odb_loose_source_write_stream(odb->sources, stream, len, oid);
 }
 
 struct object_database *odb_new(struct repository *repo)
@@ -1002,13 +1044,13 @@ struct object_database *odb_new(struct repository *repo)
 	return o;
 }
 
-static void free_object_directories(struct object_database *o)
+static void odb_free_sources(struct object_database *o)
 {
 	while (o->sources) {
 		struct odb_source *next;
 
 		next = o->sources->next;
-		free_object_directory(o->sources);
+		odb_source_free(o->sources);
 		o->sources = next;
 	}
 	kh_destroy_odb_path_map(o->source_by_path);
@@ -1026,7 +1068,7 @@ void odb_clear(struct object_database *o)
 	o->commit_graph = NULL;
 	o->commit_graph_attempted = 0;
 
-	free_object_directories(o);
+	odb_free_sources(o);
 	o->sources_tail = NULL;
 	o->loaded_alternates = 0;
 
@@ -1057,7 +1099,7 @@ void odb_reprepare(struct object_database *o)
 	odb_prepare_alternates(o);
 
 	for (source = o->sources; source; source = source->next)
-		odb_clear_loose_cache(source);
+		odb_loose_source_reprepare(source);
 
 	o->approximate_object_count_valid = 0;
 
diff --git a/odb.h b/odb.h
index e6602dd90c833c9d7c86c5e8b374c98b8db49284..5c25a37731737ba6c2d11a1852c7991507b310ad 100644
--- a/odb.h
+++ b/odb.h
@@ -14,6 +14,14 @@ struct strbuf;
 struct repository;
 struct multi_pack_index;
 
+/*
+ * Set this to 0 to prevent odb_read_object_info_extended() from fetching missing
+ * blobs. This has a difference only if extensions.partialClone is set.
+ *
+ * Its default value is 1.
+ */
+extern int fetch_if_missing;
+
 /*
  * Compute the exact path an alternate is at and returns it. In case of
  * error NULL is returned and the human readable error is added to `err`
@@ -40,20 +48,8 @@ struct odb_source {
 	/* Object database that owns this object source. */
 	struct object_database *odb;
 
-	/*
-	 * Used to store the results of readdir(3) calls when we are OK
-	 * sacrificing accuracy due to races for speed. That includes
-	 * object existence with OBJECT_INFO_QUICK, as well as
-	 * our search for unique abbreviated hashes. Don't use it for tasks
-	 * requiring greater accuracy!
-	 *
-	 * Be sure to call odb_load_loose_cache() before using.
-	 */
-	uint32_t loose_objects_subdir_seen[8]; /* 256 bits */
-	struct oidtree *loose_objects_cache;
-
-	/* Map between object IDs for loose objects. */
-	struct loose_object_map *loose_map;
+	/* Private state for loose objects. */
+	struct odb_loose_source *loose;
 
 	/*
 	 * private data
@@ -89,6 +85,10 @@ struct odb_source {
 	char *path;
 };
 
+struct odb_source *odb_source_new(struct object_database *odb,
+				  const char *path,
+				  bool local);
+
 struct packed_git;
 struct packfile_store;
 struct cached_object_entry;
@@ -396,6 +396,9 @@ int odb_has_object(struct object_database *odb,
 		   const struct object_id *oid,
 		   unsigned flags);
 
+int odb_freshen_object(struct object_database *odb,
+		       const struct object_id *oid);
+
 void odb_assert_oid_type(struct object_database *odb,
 			 const struct object_id *oid, enum object_type expect);
 
@@ -489,4 +492,14 @@ static inline int odb_write_object(struct object_database *odb,
 	return odb_write_object_ext(odb, buf, len, type, oid, NULL, 0);
 }
 
+struct odb_input_stream {
+	const void *(*read)(struct odb_input_stream *, unsigned long *len);
+	void *data;
+	int is_finished;
+};
+
+int odb_write_object_stream(struct object_database *odb,
+			    struct odb_input_stream *stream, size_t len,
+			    struct object_id *oid);
+
 #endif /* ODB_H */
diff --git a/packfile.c b/packfile.c
index 5a7caec29259771d2f15e9ac4979c0eec964251a..2ab49a0beb157ba2a53b3ad6c3ee88ac321148f4 100644
--- a/packfile.c
+++ b/packfile.c
@@ -819,6 +819,22 @@ struct packed_git *packfile_store_load_pack(struct packfile_store *store,
 	return p;
 }
 
+int packfile_store_freshen_object(struct packfile_store *store,
+				  const struct object_id *oid)
+{
+	struct pack_entry e;
+	if (!find_pack_entry(store->odb->repo, oid, &e))
+		return 0;
+	if (e.p->is_cruft)
+		return 0;
+	if (e.p->freshened)
+		return 1;
+	if (utime(e.p->pack_name, NULL))
+		return 0;
+	e.p->freshened = 1;
+	return 1;
+}
+
 void (*report_garbage)(unsigned seen_bits, const char *path);
 
 static void report_helper(const struct string_list *list,
diff --git a/packfile.h b/packfile.h
index e7a5792b6cf691453e116ce541abf6e3280066f6..0ad080046f155345d15cfbcaa0680d78dbea7938 100644
--- a/packfile.h
+++ b/packfile.h
@@ -161,6 +161,9 @@ struct list_head *packfile_store_get_packs_mru(struct packfile_store *store);
 struct packed_git *packfile_store_load_pack(struct packfile_store *store,
 					    const char *idx_path, int local);
 
+int packfile_store_freshen_object(struct packfile_store *store,
+				  const struct object_id *oid);
+
 struct pack_window {
 	struct pack_window *next;
 	unsigned char *base;
diff --git a/repository.c b/repository.c
index 6faf5c73981ebf6c520919a5475f0243f08cea87..6aaa7ba00869bf6aa0450f3fbdf27590f7439228 100644
--- a/repository.c
+++ b/repository.c
@@ -160,20 +160,24 @@ void repo_set_gitdir(struct repository *repo,
 	 * until after xstrdup(root). Then we can free it.
 	 */
 	char *old_gitdir = repo->gitdir;
+	char *objects_path = NULL;
 
 	repo->gitdir = xstrdup(gitfile ? gitfile : root);
 	free(old_gitdir);
 
 	repo_set_commondir(repo, o->commondir);
+	expand_base_dir(&objects_path, o->object_dir,
+			repo->commondir, "objects");
 
 	if (!repo->objects->sources) {
-		CALLOC_ARRAY(repo->objects->sources, 1);
-		repo->objects->sources->odb = repo->objects;
-		repo->objects->sources->local = true;
+		repo->objects->sources = odb_source_new(repo->objects,
+							objects_path, true);
 		repo->objects->sources_tail = &repo->objects->sources->next;
+		free(objects_path);
+	} else {
+		free(repo->objects->sources->path);
+		repo->objects->sources->path = objects_path;
 	}
-	expand_base_dir(&repo->objects->sources->path, o->object_dir,
-			repo->commondir, "objects");
 
 	repo->objects->sources->disable_ref_updates = o->disable_ref_updates;
 
diff --git a/streaming.c b/streaming.c
index 4b13827668e67a449860e087c45a01906126aa82..8e554abd084787bb0e58922e95f766c0af054556 100644
--- a/streaming.c
+++ b/streaming.c
@@ -230,12 +230,21 @@ static int open_istream_loose(struct git_istream *st, struct repository *r,
 			      enum object_type *type)
 {
 	struct object_info oi = OBJECT_INFO_INIT;
+	struct odb_source *source;
+
 	oi.sizep = &st->size;
 	oi.typep = type;
 
-	st->u.loose.mapped = map_loose_object(r, oid, &st->u.loose.mapsize);
+	odb_prepare_alternates(r->objects);
+	for (source = r->objects->sources; source; source = source->next) {
+		st->u.loose.mapped = odb_loose_source_map_object(source, oid,
+								 &st->u.loose.mapsize);
+		if (st->u.loose.mapped)
+			break;
+	}
 	if (!st->u.loose.mapped)
 		return -1;
+
 	switch (unpack_loose_header(&st->z, st->u.loose.mapped,
 				    st->u.loose.mapsize, st->u.loose.hdr,
 				    sizeof(st->u.loose.hdr))) {