Improve the ODB writing backend

Temporary files when doing streaming writes are now stored inside the
Objects folder, to prevent issues when moving files between
disks/partitions.

Add support for block writes to the ODB again (for those backends that
cannot implement streaming).

include/git2/odb.h

@@ -156,6 +156,26 @@ GIT_EXTERN(int) git_odb_read_header(size_t *len_p, git_otype *type_p, git_odb *d
  */
 GIT_EXTERN(int) git_odb_exists(git_odb *db, const git_oid *id);
 
+/**
+ * Write an object directly into the ODB
+ *
+ * This method writes a full object straight into the ODB.
+ * For most cases, it is preferred to write objects through a write
+ * stream, which is both faster and less memory intensive, specially
+ * for big objects.
+ *
+ * This method is provided for compatibility with custom backends
+ * which are not able to support streaming writes
+ *
+ * @param oid pointer to store the OID result of the write
+ * @param odb object database where to store the object
+ * @param data buffer with the data to storr
+ * @param len size of the buffer
+ * @param type type of the data to store
+ * @return 0 on success; error code otherwise
+ */
+GIT_EXTERN(int) git_odb_write(git_oid *oid, git_odb *odb, const void *data, size_t len, git_otype type);
+
 /**
  * Open a stream to write an object into the ODB
  *

include/git2/odb_backend.h

@@ -55,6 +55,13 @@ struct git_odb_backend {
 			struct git_odb_backend *,
 			const git_oid *);
 
+	int (* write)(
+			git_oid *,
+			struct git_odb_backend *,
+			const void *,
+			size_t,
+			git_otype);
+
 	int (* writestream)(
 			struct git_odb_stream **,
 			struct git_odb_backend *,