revision.c: refactor add_index_objects_to_pending()

The core code is factored out and take 'struct index_state *' instead so
that we can reuse it to add objects from index files other than .git/index
in the next patch.
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

revision.c

@@ -1262,13 +1262,13 @@ static void add_cache_tree(struct cache_tree *it, struct rev_info *revs,
 
 }
 
-void add_index_objects_to_pending(struct rev_info *revs, unsigned flags)
+static void do_add_index_objects_to_pending(struct rev_info *revs,
+					    struct index_state *istate)
 {
 	int i;
 
-	read_cache();
-	for (i = 0; i < active_nr; i++) {
-		struct cache_entry *ce = active_cache[i];
+	for (i = 0; i < istate->cache_nr; i++) {
+		struct cache_entry *ce = istate->cache[i];
 		struct blob *blob;
 
 		if (S_ISGITLINK(ce->ce_mode))
@@ -1281,13 +1281,19 @@ void add_index_objects_to_pending(struct rev_info *revs, unsigned flags)
 					     ce->ce_mode, ce->name);
 	}
 
-	if (active_cache_tree) {
+	if (istate->cache_tree) {
 		struct strbuf path = STRBUF_INIT;
-		add_cache_tree(active_cache_tree, revs, &path);
+		add_cache_tree(istate->cache_tree, revs, &path);
 		strbuf_release(&path);
 	}
 }
 
+void add_index_objects_to_pending(struct rev_info *revs, unsigned int flags)
+{
+	read_cache();
+	do_add_index_objects_to_pending(revs, &the_index);
+}
+
 static int add_parents_only(struct rev_info *revs, const char *arg_, int flags,
 			    int exclude_parent)
 {