Add support for incremental builds

Implement a scheme from the C tools where symbols get corresponding
files that are touch'ed whenever the symbol's value changes. This can be
used to add e.g. Makefile dependencies between source files and
particular symbols.

See the docstring of the new sync_deps() function for more information.

Piggyback a small sanity check for write_autoconf().

1 files changed, 9 insertions, 0 deletions

diff --git a/README.rst b/README.rst
index 772a3c2..c11d45c 100644
--- a/README.rst
+++ b/README.rst
@@ -34,6 +34,15 @@ configuration systems. It can do the following, among other things:
   The generated headers use the same format as ``include/generated/autoconf.h``
   from the Linux kernel.
 
+- **Implement incremental builds**
+
+  This uses the same scheme as the ``include/config`` directory in the kernel:
+  Symbols are translated into files that are touched when the symbol's value
+  changes between builds, which can be used to avoid having to do a full
+  rebuild whenever the configuration is changed.
+
+  See the ``sync_deps()`` function for more information.
+
 - **Inspect symbols**
 
   Printing a symbol gives output which could be fed back into a Kconfig parser