Leave unchanged output files untouched

Before writing a configuration file or header file, compare the old
contents of the file against the new contents. If there's no change,
skip the write, to avoid updating the file modification time.

This might avoid triggering redundant rebuilds depending on how the
build system is set up, and could allow for a simpler setup.

1 files changed, 5 insertions, 0 deletions

diff --git a/README.rst b/README.rst
index 0ed074f..a6d4a8d 100644
--- a/README.rst
+++ b/README.rst
@@ -149,6 +149,11 @@ Getting started
    ``config.h``.
 
    Normally, ``genconfig`` would be run automatically as part of the build.
+
+   Before writing a header file or other configuration output, Kconfiglib
+   compares the old contents of the file against the new contents. If there's
+   no change, the write is skipped. This avoids updating file metadata like the
+   modification time, and might save work depending on your build setup.
    
    Adding new configuration output formats should be relatively straightforward.
    See the implementation of ``write_config()`` in `kconfiglib.py