Introduce explicit hidden target configuration class in manual

1 files changed, 10 insertions, 7 deletions

diff --git a/doc/manual.cli b/doc/manual.cli
index 3a00e2d..c584b2c 100644
--- a/doc/manual.cli
+++ b/doc/manual.cli
@@ -2179,13 +2179,16 @@ to detect warnings in the logs.
 The build target configurations can belong to multiple classes with their
 names reflecting some common configuration aspects, such as the operating
 system, compiler, build options, etc. Predefined class names are \c{default},
-\c{all}, \c{none}, \c{host}, and \c{build2}. The default target configurations
-are built by default. A configuration must also belong to the \c{all} unless
-it is hidden. A configuration that is self-hosted must also belong to the
-\c{host} class and, if it is also self-hosted for build system modules, to the
-\c{build2} class. Valid custom class names must contain only alpha-numeric
-characters, \c{_}, \c{+}, \c{-}, and \c{.}, except as the first character for
-the last three. Class names that start with \c{_} are reserved for the future
+\c{all}, \c{hidden}, \c{none}, \c{host}, and \c{build2}. The default target
+configurations are built by default. A configuration must also belong to the
+\c{all}, \c{hidden}, or some special-purpose configuration class. The latter
+is intended for testing some optional functionality which packages are not
+expected to provide normally (for example, relocatable installation). A
+configuration that is self-hosted must also belong to the \c{host} class and,
+if it is also self-hosted for build system modules, to the \c{build2}
+class. Valid custom class names must contain only alpha-numeric characters,
+\c{_}, \c{+}, \c{-}, and \c{.}, except as the first character for the last
+three. Class names that start with \c{_} are reserved for the future
 hidden/special class functionality.
 
 Regular expressions must start with \c{~}, to be distinguished from target