+`[oot]`: Out-of-tree build support
+----------------------------------
+
+ * `dir`: The build directory. If relative, it is relative to the
+ parent of the invocation directory (and could be a symlink then).
+ Default is `Build` (assuming `use` is specified).
+
+ * `use`: How to become the build user. Needs to be combined
+ with other setting(s):
+
+ * `ssh`: Use ssh. `user` must be given as well and can be
+ a username on localhost, or the `<user>@<host>`
+ argument to ssh.
+
+ * `command_args`: `command` must be specified as a list,
+ specifying a command and arguments which work like `nice`.
+
+ * `command_sh`: `command` must be specified as a list,
+ specifying a command and arguments which work like `sh -c`.
+
+ * `null`: Run builds as the same user.
+
+ * `really`: Use `really` from `chiark-really.deb`.
+ `user` must be given as well.
+
+ * `command`: The command to run for `command_sh` or `command_args`.
+
+ * `user`: The local username for `really` and `ssh`, or
+ `<user>@<host>` for `ssh`.
+