configure_file: Add support for indented cmakedefine

Optional spaces and/or tabs are now understood between the '#' character
and the 'cmakedefine'/'cmakedefine01' words. This indentation is
preserved in the output lines.

Fixes: #13037

1 files changed, 12 insertions, 0 deletions

diff --git a/Help/command/configure_file.rst b/Help/command/configure_file.rst
index 4304f09..75ec441 100644
--- a/Help/command/configure_file.rst
+++ b/Help/command/configure_file.rst
@@ -30,6 +30,18 @@ a false constant by the :command:`if` command.  The "..." content on the
 line after the variable name, if any, is processed as above.
 Input file lines of the form ``#cmakedefine01 VAR`` will be replaced with
 either ``#define VAR 1`` or ``#define VAR 0`` similarly.
+The result lines (with the exception of the ``#undef`` comments) can be
+indented using spaces and/or tabs between the ``#`` character
+and the ``cmakedefine`` or ``cmakedefine01`` words. This whitespace
+indentation will be preserved in the output lines::
+
+  #  cmakedefine VAR
+  #  cmakedefine01 VAR
+
+will be replaced, if ``VAR`` is defined, with::
+
+  #  define VAR
+  #  define VAR 1
 
 If the input file is modified the build system will re-run CMake to
 re-configure the file and generate the build system again.