rebase: fix a memory leak

buf was never freed.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/rebase.c b/builtin/rebase.c
index cd233c6..a9062c6 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -2165,6 +2165,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	ret = !!run_specific_rebase(&options, action);
 
 cleanup:
+	strbuf_release(&buf);
 	strbuf_release(&revisions);
 	free(options.head_name);
 	free(options.gpg_sign_opt);