Update doc

doc/jbuild.rst

@@ -843,6 +843,10 @@ syntax:
 - ``(file <filename>)`` or simply ``<filename>``: depend on this file
 - ``(alias <alias-name>)``: depend on the construction of this alias, for
   instance: ``(alias src/runtest)``
+- ``(alias_rec <alias-name>)``: depend on the construction of this
+  alias recursively in all children directories wherever it is
+  defined. For instance: ``(alias_rec src/runtest)`` might depend on
+  ``(alias src/runtest)``, ``(alias src/foo/bar/runtest)``, ...
 - ``(glob_files <glob>)``: depend on all files matched by ``<glob>``, see the
   :ref:`glob <glob>` for details
 - ``(files_recursively_in <dir>)``: depend on all files in the subtree with root

doc/terminology.rst

@@ -43,11 +43,12 @@ Terminology
 -  **build context root**: the root of a build context named ``foo`` is
    ``<root>/_build/<foo>``
 
--  **alias**: an alias is a build target that doesn't produce any file
-   and has configurable dependencies. Alias are per-directory and some
-   are recursive; asking an alias to be built in a given directory will
-   trigger the construction of the alias in all children directories
-   recursively. The most interesting ones are:
+- **alias**: an alias is a build target that doesn't produce any file
+   and has configurable dependencies. Aliases are
+   per-directory. However, on the command line, asking for an alias to
+   be built in a given directory will trigger the construction of the
+   alias in all children directories recursively. Jbuilder defines the
+   following standard aliases:
 
    -  ``runtest`` which runs user defined tests
    -  ``install`` which depends on everything that should be installed

doc/usage.rst

@@ -125,8 +125,9 @@ Aliases
 -------
 
 Targets starting with a ``@`` are interpreted as aliases. For instance
-``@src/runtest`` means the alias ``src/runtest``. If you want to refer
-to a target starting with a ``@``, simply write: ``./@foo``.
+``@src/runtest`` means the alias ``runtest`` in all descendant of
+``src`` where it is defined. If you want to refer to a target starting
+with a ``@``, simply write: ``./@foo``.
 
 Note that an alias not pointing to the ``_build`` directory always
 depends on all the corresponding aliases in build contexts.