reftable: pass opts as constant pointer

We sometimes pass the refatble write options as value and sometimes as a
pointer. This is quite confusing and makes the reader wonder whether the
options get modified sometimes.

In fact, `reftable_new_writer()` does cause the caller-provided options
to get updated when some values aren't set up. This is quite unexpected,
but didn't cause any harm until now.

Adapt the code so that we do not modify the caller-provided values
anymore. While at it, refactor the code to code to consistently pass the
options as a constant pointer to clarify that the caller-provided opts
will not ever get modified.

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

1 files changed, 5 insertions, 2 deletions

diff --git a/reftable/stack.c b/reftable/stack.c
index 54e7473f3a..d2e68be7e8 100644
--- a/reftable/stack.c
+++ b/reftable/stack.c
@@ -54,12 +54,15 @@ static int reftable_fd_flush(void *arg)
 }
 
 int reftable_new_stack(struct reftable_stack **dest, const char *dir,
-		       struct reftable_write_options opts)
+		       const struct reftable_write_options *_opts)
 {
 	struct reftable_stack *p = reftable_calloc(1, sizeof(*p));
 	struct strbuf list_file_name = STRBUF_INIT;
+	struct reftable_write_options opts = {0};
 	int err = 0;
 
+	if (_opts)
+		opts = *_opts;
 	if (opts.hash_id == 0)
 		opts.hash_id = GIT_SHA1_FORMAT_ID;
 
@@ -1438,7 +1441,7 @@ int reftable_stack_print_directory(const char *stackdir, uint32_t hash_id)
 	struct reftable_merged_table *merged = NULL;
 	struct reftable_table table = { NULL };
 
-	int err = reftable_new_stack(&stack, stackdir, opts);
+	int err = reftable_new_stack(&stack, stackdir, &opts);
 	if (err < 0)
 		goto done;