read_index_from(): catch out of order entries when reading an index file

Signed-off-by: Jaime Soriano Pastor <jsorianopastor@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

read-cache.c

@@ -1438,6 +1438,21 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk,
 	return ce;
 }
 
+static void check_ce_order(struct cache_entry *ce, struct cache_entry *next_ce)
+{
+	int name_compare = strcmp(ce->name, next_ce->name);
+	if (0 < name_compare)
+		die("unordered stage entries in index");
+	if (!name_compare) {
+		if (!ce_stage(ce))
+			die("multiple stage entries for merged file '%s'",
+				ce->name);
+		if (ce_stage(ce) > ce_stage(next_ce))
+			die("unordered stage entries for '%s'",
+				ce->name);
+	}
+}
+
 /* remember to discard_cache() before reading a different cache! */
 int read_index_from(struct index_state *istate, const char *path)
 {
@@ -1499,6 +1514,9 @@ int read_index_from(struct index_state *istate, const char *path)
 		ce = create_from_disk(disk_ce, &consumed, previous_name);
 		set_index_entry(istate, i, ce);
 
+		if (i > 0)
+			check_ce_order(istate->cache[i - 1], ce);
+
 		src_offset += consumed;
 	}
 	strbuf_release(&previous_name_buf);