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, 9 insertions, 1 deletions

diff --git a/genconfig.py b/genconfig.py
index c575c9a..ba2bb73 100755
--- a/genconfig.py
+++ b/genconfig.py
@@ -7,10 +7,18 @@
 Generates a header file with #defines from the configuration, matching the
 format of include/generated/autoconf.h in the Linux kernel.
 
-Optionally creates/updates a directory structure with one file per symbol that
+Optionally, also writes the configuration output as a .config file. See
+--config-out.
+
+Optionally, creates/updates a directory structure with one file per symbol that
 can be used to implement incremental builds. See the docstring for
 Kconfig.sync_deps() in kconfiglib.py.
 
+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.
+
 By default, the configuration is generated from '.config'. A different
 configuration file can be passed in the KCONFIG_CONFIG environment variable.
 """