ui-shared: rename parameter to cgit_print_snapshot_links()

This is expected to be a ref not a hex object ID, so name it more
appropriately.

Signed-off-by: John Keeping <john@keeping.me.uk>
Reviewed-by: Christian Hesse <mail@eworm.de>
diff --git a/ui-shared.c b/ui-shared.c
index d638bf4..8ae81d2 100644
--- a/ui-shared.c
+++ b/ui-shared.c
@@ -1111,13 +1111,13 @@
 	strbuf_addf(filename, "%s-%s", base, ref);
 }
 
-void cgit_print_snapshot_links(const struct cgit_repo *repo, const char *hex)
+void cgit_print_snapshot_links(const struct cgit_repo *repo, const char *ref)
 {
 	const struct cgit_snapshot_format* f;
 	struct strbuf filename = STRBUF_INIT;
 	size_t prefixlen;
 
-	cgit_compose_snapshot_prefix(&filename, cgit_snapshot_prefix(repo), hex);
+	cgit_compose_snapshot_prefix(&filename, cgit_snapshot_prefix(repo), ref);
 	prefixlen = filename.len;
 	for (f = cgit_snapshot_formats; f->suffix; f++) {
 		if (!(repo->snapshots & f->bit))