+- **`DATADIR`:**
+ If set to the location of a directory, ⛩📰 书社 will run a two‐stage build.
+ In the first stage, only files in `SRCDIR` which match `FINDDATARULES` (see below) will be built, with files in `DATADIR` serving as includes.
+ In the second stage, the remaining files in `SRCDIR` will be built, with the files built during the first stage, in addition to any files in `INCLUDEDIR`, serving as includes.
+ Files built during the first stage are copied into `DESTDIR` alongside those from the second stage when installing.
+
+ This functionality is intended for sites where the bulk of the site can be built from a few data files which are expensive to create.
+