Help: Clarify version specification in CMAKE_GENERATOR_INSTANCE

Improve the documentation added by commit ec8d37b3b1 (VS: Support
version specification in CMAKE_GENERATOR_INSTANCE, 2021-10-26,
v3.23.0-rc1~452^2~1).

Fixes: #23225

1 files changed, 22 insertions, 5 deletions

diff --git a/Help/variable/CMAKE_GENERATOR_INSTANCE.rst b/Help/variable/CMAKE_GENERATOR_INSTANCE.rst
index 6a35f17786..6bfabe0515 100644
--- a/Help/variable/CMAKE_GENERATOR_INSTANCE.rst
+++ b/Help/variable/CMAKE_GENERATOR_INSTANCE.rst
@@ -39,16 +39,33 @@ The ``key=value`` pairs form a comma-separated list of options to
 specify details of the instance selection.
 Supported pairs are:
 
-``version=<major>.<minor>.<MMMDD>.<BBB>``
+``version=<major>.<minor>.<date>.<build>``
   .. versionadded:: 3.23
 
-  Specify the 4-component VS Build Version.
+  Specify the 4-component VS Build Version, a.k.a. Build Number.
+  The components are:
+
+  ``<major>.<minor>``
+
+    The VS major and minor version numbers.
+    These are the same as the release version numbers.
+
+  ``<date>``
+
+    A build date in the format ``MMMDD``, where ``MMM`` is a month index
+    since an epoch used by Microsoft, and ``DD`` is a day in that month.
+
+  ``<build>``
+
+    A build index on the day represented by ``<date>``.
+
+  The build number is reported by ``vswhere`` as ``installationVersion``.
+  For example, VS 16.11.10 has build number ``16.11.32126.315``.
 
 .. versionadded:: 3.23
 
-  A portable VS instance may be specified that is not known to the
-  Visual Studio Installer tool.  The ``location`` and ``version=``
-  values must both be provided.
+  A portable VS instance, which is not known to the Visual Studio Installer,
+  may be specified by providing both ``location`` and ``version=``.
 
 If the value of ``CMAKE_GENERATOR_INSTANCE`` is not specified explicitly
 by the user or a toolchain file, CMake queries the Visual Studio Installer