commit-graph: free write-context base_graph_name during cleanup

Commit 6c622f9f0b (commit-graph: write commit-graph chains, 2019-06-18)
added a base_graph_name string to the write_commit_graph_context struct.
But the end-of-function cleanup forgot to free it, causing a leak.

This (presumably in combination with the preceding leak-fixes) lets us
mark t5328 as leak-free.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit-graph.c

@@ -2518,6 +2518,7 @@ int write_commit_graph(struct object_directory *odb,
 
 cleanup:
 	free(ctx->graph_name);
+	free(ctx->base_graph_name);
 	free(ctx->commits.list);
 	oid_array_clear(&ctx->oids);
 	clear_topo_level_slab(&topo_levels);

t/t5328-commit-graph-64bit-time.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='commit graph with 64-bit timestamps'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 if ! test_have_prereq TIME_IS_64BIT || ! test_have_prereq TIME_T_IS_64BIT