diff --git a/builtin/grep.c b/builtin/grep.c
index 77f0c4dc90..d3d86abe01 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -25,12 +25,11 @@
 #include "setup.h"
 #include "submodule.h"
 #include "submodule-config.h"
-#include "object-file.h"
 #include "object-name.h"
 #include "odb.h"
+#include "odb/source.h"
 #include "oid-array.h"
 #include "oidset.h"
-#include "packfile.h"
 #include "pager.h"
 #include "path.h"
 #include "promisor-remote.h"
@@ -1357,15 +1356,8 @@ int cmd_grep(int argc,
 		if (recurse_submodules)
 			repo_read_gitmodules(the_repository, 1);
 
-		if (startup_info->have_repository) {
-			struct odb_source *source;
-
-			odb_prepare_alternates(the_repository->objects);
-			for (source = the_repository->objects->sources; source; source = source->next) {
-				struct odb_source_files *files = odb_source_files_downcast(source);
-				odb_source_packed_prepare(files->packed);
-			}
-		}
+		if (startup_info->have_repository)
+			odb_prepare(the_repository->objects, 0);
 
 		start_threads(&opt);
 	} else {
diff --git a/midx.c b/midx.c
index cc6b94f9dd..76c3f92cc3 100644
--- a/midx.c
+++ b/midx.c
@@ -101,7 +101,7 @@ static int midx_read_object_offsets(const unsigned char *chunk_start,
 
 struct multi_pack_index *get_multi_pack_index(struct odb_source_packed *source)
 {
-	odb_source_packed_prepare(source);
+	odb_source_prepare(&source->base, 0);
 	return source->midx;
 }
 
diff --git a/odb.c b/odb.c
index 7d555be09f..68dca6357f 100644
--- a/odb.c
+++ b/odb.c
@@ -1070,7 +1070,7 @@ void odb_free(struct object_database *o)
 	free(o);
 }
 
-void odb_reprepare(struct object_database *o)
+void odb_prepare(struct object_database *o, enum odb_prepare_flags flags)
 {
 	struct odb_source *source;
 
@@ -1082,13 +1082,19 @@ void odb_reprepare(struct object_database *o)
 	 * the linked list, so existing odbs will continue to exist for
 	 * the lifetime of the process.
 	 */
-	o->loaded_alternates = 0;
+	if (flags & ODB_PREPARE_FLUSH_CACHES) {
+		o->loaded_alternates = 0;
+		o->object_count_valid = 0;
+	}
+
 	odb_prepare_alternates(o);
-
 	for (source = o->sources; source; source = source->next)
-		odb_source_reprepare(source);
-
-	o->object_count_valid = 0;
+		odb_source_prepare(source, flags);
 
 	obj_read_unlock();
 }
+
+void odb_reprepare(struct object_database *o)
+{
+	odb_prepare(o, ODB_PREPARE_FLUSH_CACHES);
+}
diff --git a/odb.h b/odb.h
index 3834a0dcbf..a194865052 100644
--- a/odb.h
+++ b/odb.h
@@ -124,10 +124,22 @@ void odb_free(struct object_database *o);
  */
 void odb_close(struct object_database *o);
 
+enum odb_prepare_flags {
+	/*
+	 * Flush caches, reload alternates and then re-prepare each object
+	 * source so that new objects may become accessible.
+	 */
+	ODB_PREPARE_FLUSH_CACHES = (1 << 0),
+};
+
 /*
- * Clear caches, reload alternates and then reload object sources so that new
- * objects may become accessible.
+ * Prepare the object database for use. Calling this function is generally not
+ * needed, but can be useful in case the caller wants to pre-open individual
+ * sources.
  */
+void odb_prepare(struct object_database *o, enum odb_prepare_flags flags);
+
+/* Equivalent to `odb_prepare(o, ODB_PREPARE_FLUSH_CACHES)`. */
 void odb_reprepare(struct object_database *o);
 
 /*
diff --git a/odb/source-files.c b/odb/source-files.c
index bbd1784b33..6c8e935c75 100644
--- a/odb/source-files.c
+++ b/odb/source-files.c
@@ -41,11 +41,12 @@ static void odb_source_files_close(struct odb_source *source)
 	odb_source_close(&files->packed->base);
 }
 
-static void odb_source_files_reprepare(struct odb_source *source)
+static void odb_source_files_prepare(struct odb_source *source,
+				     enum odb_prepare_flags flags)
 {
 	struct odb_source_files *files = odb_source_files_downcast(source);
-	odb_source_reprepare(&files->loose->base);
-	odb_source_reprepare(&files->packed->base);
+	odb_source_prepare(&files->loose->base, flags);
+	odb_source_prepare(&files->packed->base, flags);
 }
 
 static int odb_source_files_read_object_info(struct odb_source *source,
@@ -273,7 +274,7 @@ struct odb_source_files *odb_source_files_new(struct object_database *odb,
 
 	files->base.free = odb_source_files_free;
 	files->base.close = odb_source_files_close;
-	files->base.reprepare = odb_source_files_reprepare;
+	files->base.prepare = odb_source_files_prepare;
 	files->base.read_object_info = odb_source_files_read_object_info;
 	files->base.read_object_stream = odb_source_files_read_object_stream;
 	files->base.for_each_object = odb_source_files_for_each_object;
diff --git a/odb/source-inmemory.c b/odb/source-inmemory.c
index 7f1b6f4636..0b51c58238 100644
--- a/odb/source-inmemory.c
+++ b/odb/source-inmemory.c
@@ -325,7 +325,8 @@ static void odb_source_inmemory_close(struct odb_source *source UNUSED)
 {
 }
 
-static void odb_source_inmemory_reprepare(struct odb_source *source UNUSED)
+static void odb_source_inmemory_prepare(struct odb_source *source UNUSED,
+					enum odb_prepare_flags flags UNUSED)
 {
 }
 
@@ -365,7 +366,7 @@ struct odb_source_inmemory *odb_source_inmemory_new(struct object_database *odb)
 
 	source->base.free = odb_source_inmemory_free;
 	source->base.close = odb_source_inmemory_close;
-	source->base.reprepare = odb_source_inmemory_reprepare;
+	source->base.prepare = odb_source_inmemory_prepare;
 	source->base.read_object_info = odb_source_inmemory_read_object_info;
 	source->base.read_object_stream = odb_source_inmemory_read_object_stream;
 	source->base.for_each_object = odb_source_inmemory_for_each_object;
diff --git a/odb/source-loose.c b/odb/source-loose.c
index 6211348a4d..a404046d50 100644
--- a/odb/source-loose.c
+++ b/odb/source-loose.c
@@ -664,10 +664,12 @@ static void odb_source_loose_clear_cache(struct odb_source_loose *loose)
 	       sizeof(loose->subdir_seen));
 }
 
-static void odb_source_loose_reprepare(struct odb_source *source)
+static void odb_source_loose_prepare(struct odb_source *source,
+				     enum odb_prepare_flags flags)
 {
 	struct odb_source_loose *loose = odb_source_loose_downcast(source);
-	odb_source_loose_clear_cache(loose);
+	if (flags & ODB_PREPARE_FLUSH_CACHES)
+		odb_source_loose_clear_cache(loose);
 }
 
 static void odb_source_loose_close(struct odb_source *source UNUSED)
@@ -708,7 +710,7 @@ struct odb_source_loose *odb_source_loose_new(struct object_database *odb,
 
 	loose->base.free = odb_source_loose_free;
 	loose->base.close = odb_source_loose_close;
-	loose->base.reprepare = odb_source_loose_reprepare;
+	loose->base.prepare = odb_source_loose_prepare;
 	loose->base.read_object_info = odb_source_loose_read_object_info;
 	loose->base.read_object_stream = odb_source_loose_read_object_stream;
 	loose->base.for_each_object = odb_source_loose_for_each_object;
diff --git a/odb/source-packed.c b/odb/source-packed.c
index 06b31dd743..a0259b95bf 100644
--- a/odb/source-packed.c
+++ b/odb/source-packed.c
@@ -15,7 +15,7 @@ static int find_pack_entry(struct odb_source_packed *store,
 {
 	struct packfile_list_entry *l;
 
-	odb_source_packed_prepare(store);
+	odb_source_prepare(&store->base, 0);
 	if (store->midx && fill_midx_entry(store->midx, oid, e))
 		return 1;
 
@@ -47,7 +47,7 @@ static int odb_source_packed_read_object_info(struct odb_source *source,
 	 * been added since the last time we have prepared the packfile store.
 	 */
 	if (flags & OBJECT_INFO_SECOND_READ)
-		odb_source_reprepare(source);
+		odb_source_prepare(source, ODB_PREPARE_FLUSH_CACHES);
 
 	if (!find_pack_entry(packed, oid, &e))
 		return 1;
@@ -692,27 +692,25 @@ static int sort_pack(const struct packfile_list_entry *a,
 	return -1;
 }
 
-void odb_source_packed_prepare(struct odb_source_packed *source)
-{
-	if (source->initialized)
-		return;
-
-	prepare_multi_pack_index_one(source);
-	prepare_packed_git_one(source);
-
-	sort_packs(&source->packs.head, sort_pack);
-	for (struct packfile_list_entry *e = source->packs.head; e; e = e->next)
-		if (!e->next)
-			source->packs.tail = e;
-
-	source->initialized = true;
-}
-
-static void odb_source_packed_reprepare(struct odb_source *source)
+static void odb_source_packed_prepare(struct odb_source *source,
+				      enum odb_prepare_flags flags)
 {
 	struct odb_source_packed *packed = odb_source_packed_downcast(source);
-	packed->initialized = false;
-	odb_source_packed_prepare(packed);
+
+	if (flags & ODB_PREPARE_FLUSH_CACHES)
+		packed->initialized = false;
+	if (packed->initialized)
+		return;
+
+	prepare_multi_pack_index_one(packed);
+	prepare_packed_git_one(packed);
+
+	sort_packs(&packed->packs.head, sort_pack);
+	for (struct packfile_list_entry *e = packed->packs.head; e; e = e->next)
+		if (!e->next)
+			packed->packs.tail = e;
+
+	packed->initialized = true;
 }
 
 static void odb_source_packed_reparent(const char *name UNUSED,
@@ -768,7 +766,7 @@ struct odb_source_packed *odb_source_packed_new(struct object_database *odb,
 
 	packed->base.free = odb_source_packed_free;
 	packed->base.close = odb_source_packed_close;
-	packed->base.reprepare = odb_source_packed_reprepare;
+	packed->base.prepare = odb_source_packed_prepare;
 	packed->base.read_object_info = odb_source_packed_read_object_info;
 	packed->base.read_object_stream = odb_source_packed_read_object_stream;
 	packed->base.for_each_object = odb_source_packed_for_each_object;
diff --git a/odb/source-packed.h b/odb/source-packed.h
index f0724b204c..77309ddd09 100644
--- a/odb/source-packed.h
+++ b/odb/source-packed.h
@@ -82,13 +82,4 @@ static inline struct odb_source_packed *odb_source_packed_downcast(struct odb_so
 	return container_of(source, struct odb_source_packed, base);
 }
 
-/*
- * Prepare the source by loading packfiles and multi-pack indices for
- * all alternates. This becomes a no-op if the source is already prepared.
- *
- * It shouldn't typically be necessary to call this function directly, as
- * functions that access the source know to prepare it.
- */
-void odb_source_packed_prepare(struct odb_source_packed *source);
-
 #endif
diff --git a/odb/source.h b/odb/source.h
index 8767708c9c..efeff7ed12 100644
--- a/odb/source.h
+++ b/odb/source.h
@@ -83,11 +83,12 @@ struct odb_source {
 	void (*close)(struct odb_source *source);
 
 	/*
-	 * This callback is expected to clear underlying caches of the object
-	 * database source. The function is called when the repository has for
-	 * example just been repacked so that new objects will become visible.
+	 * This callback is expected to prepare the source so that it becomes
+	 * ready for use. It optionally clears underlying caches of the object
+	 * database source.
 	 */
-	void (*reprepare)(struct odb_source *source);
+	void (*prepare)(struct odb_source *source,
+			enum odb_prepare_flags flags);
 
 	/*
 	 * This callback is expected to read object information from the object
@@ -308,13 +309,14 @@ static inline void odb_source_close(struct odb_source *source)
 }
 
 /*
- * Reprepare the object database source and clear any caches. Depending on the
+ * Prepare the object database source and clear any caches. Depending on the
  * backend used this may have the effect that concurrently-written objects
  * become visible.
  */
-static inline void odb_source_reprepare(struct odb_source *source)
+static inline void odb_source_prepare(struct odb_source *source,
+				      enum odb_prepare_flags flags)
 {
-	source->reprepare(source);
+	source->prepare(source, flags);
 }
 
 /*
diff --git a/packfile.c b/packfile.c
index 1d1b23b6cc..60dd0f286a 100644
--- a/packfile.c
+++ b/packfile.c
@@ -855,7 +855,7 @@ void for_each_file_in_pack_dir(const char *objdir,
 
 struct packfile_list_entry *packfile_store_get_packs(struct odb_source_packed *store)
 {
-	odb_source_packed_prepare(store);
+	odb_source_prepare(&store->base, 0);
 
 	if (store->midx) {
 		struct multi_pack_index *m = store->midx;