midx-write: fix leaking buffer

The buffer used to compute the final MIDX name is never released. Plug
this memory leak.

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

midx-write.c

@@ -1445,6 +1445,8 @@ static int write_midx_internal(const char *object_dir,
 			return -1;
 		}
 
+		strbuf_release(&final_midx_name);
+
 		keep_hashes[ctx.num_multi_pack_indexes_before] =
 			xstrdup(hash_to_hex(midx_hash));
 

t/t5334-incremental-multi-pack-index.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='incremental multi-pack-index'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-midx.sh