unpack-trees: don't shadow global var the_index

This function mark_new_skip_worktree() has an argument named the_index
which is also the name of a global variable. While they have different
types (the global the_index is not a pointer) mistakes can easily
happen and it's also confusing for readers. Rename the function
argument to something other than the_index.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

unpack-trees.c

@@ -1238,7 +1238,7 @@ static int clear_ce_flags(struct cache_entry **cache, int nr,
  * Set/Clear CE_NEW_SKIP_WORKTREE according to $GIT_DIR/info/sparse-checkout
  */
 static void mark_new_skip_worktree(struct exclude_list *el,
-				   struct index_state *the_index,
+				   struct index_state *istate,
 				   int select_flag, int skip_wt_flag)
 {
 	int i;
@@ -1247,8 +1247,8 @@ static void mark_new_skip_worktree(struct exclude_list *el,
 	 * 1. Pretend the narrowest worktree: only unmerged entries
 	 * are checked out
 	 */
-	for (i = 0; i < the_index->cache_nr; i++) {
-		struct cache_entry *ce = the_index->cache[i];
+	for (i = 0; i < istate->cache_nr; i++) {
+		struct cache_entry *ce = istate->cache[i];
 
 		if (select_flag && !(ce->ce_flags & select_flag))
 			continue;
@@ -1263,8 +1263,7 @@ static void mark_new_skip_worktree(struct exclude_list *el,
 	 * 2. Widen worktree according to sparse-checkout file.
 	 * Matched entries will have skip_wt_flag cleared (i.e. "in")
 	 */
-	clear_ce_flags(the_index->cache, the_index->cache_nr,
-		       select_flag, skip_wt_flag, el);
+	clear_ce_flags(istate->cache, istate->cache_nr, select_flag, skip_wt_flag, el);
 }
 
 static int verify_absent(const struct cache_entry *,