migrate.sh: Backup in single location

migrate.sh

@@ -5,6 +5,7 @@ set -e
 inventory=$1
 
 tmp_dir=/tmp/apache-require
+backup_dir=$tmp_dir/backup
 inventory=$tmp_dir/inventory
 to_convert=$tmp_dir/to_convert
 
@@ -12,7 +13,8 @@ to_convert=$tmp_dir/to_convert
 backup() {
     file=$1
 
-    cp "$file" "$file".apreq.bak
+    install --preserve-timestamps --preserve-contex \
+        -D "$file" "$backup_dir/$file"
 }
 
 verify_migration() {