Hi again,

How about this variant of the initial script?  I think it addresses the
main issues we discussed here:

  1. By default it doesn’t re-add the source in the store, so wrong
     commit/hash issues are caught when running ‘guix build guix’.

  2. It diagnoses dirty trees early on.  It does not explicitly diagnose
     missing upstream commits though, but again they’re caught when
     running ‘guix build guix’.

WDYT?

Sorry for all the back-and-forth on what looks like a tiny issue.  I do
think we’re making progress anyway!

Thanks,
Ludo’.