odb/source: make `free()` function pluggable

Introduce a new callback function in `struct odb_source` to make the
function pluggable.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/odb/source.h b/odb/source.h
index 45b72b81a0..4973fb4251 100644
--- a/odb/source.h
+++ b/odb/source.h
@@ -51,6 +51,12 @@ struct odb_source {
 	 * the current working directory.
 	 */
 	char *path;
+
+	/*
+	 * This callback is expected to free the underlying object database source and
+	 * all associated resources. The function will never be called with a NULL pointer.
+	 */
+	void (*free)(struct odb_source *source);
 };
 
 /*