@@ -1005,8 +1005,8 @@ int odb_write_object_ext(struct object_database *odb,
 			 struct object_id *compat_oid,
 			 unsigned flags)
 {
-	return odb_source_loose_write_object(odb->sources, buf, len, type,
-					     oid, compat_oid, flags);
+	return odb_source_write_object(odb->sources, buf, len, type,
+				       oid, compat_oid, flags);
 }
 
 int odb_write_object_stream(struct object_database *odb,

@@ -98,6 +98,17 @@ static int odb_source_files_freshen_object(struct odb_source *source,
 	return 0;
 }
 
+static int odb_source_files_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,
+					 unsigned flags)
+{
+	return odb_source_loose_write_object(source, buf, len, type,
+					     oid, compat_oid, flags);
+}
+
 struct odb_source_files *odb_source_files_new(struct object_database *odb,
 					      const char *path,
 					      bool local)

@@ -116,6 +127,7 @@ struct odb_source_files *odb_source_files_new(struct object_database *odb,
 	files->base.read_object_stream = odb_source_files_read_object_stream;
 	files->base.for_each_object = odb_source_files_for_each_object;
 	files->base.freshen_object = odb_source_files_freshen_object;
+	files->base.write_object = odb_source_files_write_object;
 
 	/*
 	 * Ideally, we would only ever store absolute paths in the source. This

@@ -1,6 +1,8 @@
 #ifndef ODB_SOURCE_H
 #define ODB_SOURCE_H
 
+#include "object.h"
+
 enum odb_source_type {
 	/*
 	 * The "unknown" type, which should never be in use. This type mostly

@@ -198,6 +200,24 @@ struct odb_source {
 	 */
 	int (*freshen_object)(struct odb_source *source,
 			      const struct object_id *oid);
+
+	/*
+	 * This callback is expected to persist the given object into the
+	 * object source. In case the object already exists it shall be
+	 * freshened.
+	 *
+	 * The flags field is a combination of `WRITE_OBJECT` flags.
+	 *
+	 * The resulting object ID (and optionally the compatibility object ID)
+	 * shall be written into the out pointers. The callback is expected to
+	 * return 0 on success, a negative error code otherwise.
+	 */
+	int (*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,
+			    unsigned flags);
 };
 
 /*

@@ -320,4 +340,20 @@ static inline int odb_source_freshen_object(struct odb_source *source,
 	return source->freshen_object(source, oid);
 }
 
+/*
+ * Write an object into the object database source. Returns 0 on success, a
+ * negative error code otherwise. Populates the given out pointers for the
+ * object ID and the compatibility object ID, if non-NULL.
+ */
+static inline int odb_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,
+					  unsigned flags)
+{
+	return source->write_object(source, buf, len, type, oid,
+				    compat_oid, flags);
+}
+
 #endif