>
> So long as the timestamps of your inputs are fixed, the output should
> not vary. I would be interested to hear if this solves the problem for you.
It changes the problem to one of managing timestamps of files. This is
probably easier than the current situation, but not completely trivial,
since e.g. both git checkout and build systems that copy files will
modify timestamps.
Agreed, this basically means that you have to do a 'find -exec touch -d @0 '{}' +' or so before every build. That's doable, but increases complexity and can be brittle if e.g. the filesystem doesn't have accurate mtimes or something else modifies the input files. Preferably builds should only depend on relative file names and file contents, not other kinds of metadata.