Get scons to generate a new build number
问题 I'd like to get scons to read a previous version number from a file, update a source file with a new version number and current date and then write the number back to the original file ready for the next build. This needs to happen only when the target is out of date. IOW the version number doesn't change if no build takes place. The original file is source controlled and isn't a source file else it could trigger another build on check-in (due to CI). CLARIFICATION From scons' point of view