read-cache: use index state repository for trace2 logging

Replace uses of the_repository in trace2_data_intmax() with
istate->repo, which represents the repository associated with
the index state.

This avoids relying on global repository state and aligns with
other parts of the codebase (e.g., sparse-index.c) that pass the
repository instance explicitly.

No functional change intended.

Signed-off-by: jayesh0104 <jayeshdaga99@gmail.com>

Author: jayesh0104

read-cache.c

@@ -2206,6 +2206,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	size_t extension_offset = 0;
 	int nr_threads, cpus;
 	struct index_entry_offset_table *ieot = NULL;
+	struct repository *r;
 
 	if (istate->initialized)
 		return istate->cache_nr;
@@ -2313,9 +2314,10 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	 * TODO trace2: replace "the_repository" with the actual repo instance
 	 * that is associated with the given "istate".
 	 */
-	trace2_data_intmax("index", the_repository, "read/version",
+	r = istate->repo ? istate->repo : the_repository;
+	trace2_data_intmax("index", r, "read/version",
 			   istate->version);
-	trace2_data_intmax("index", the_repository, "read/cache_nr",
+	trace2_data_intmax("index", r, "read/cache_nr",
 			   istate->cache_nr);
 
 	/*