Debian and SOURCE_DATE_EPOCH=0

[Simon Josefsson]

Janneke Nieuwenhuizen <janneke at gnu.org> writes:

> So my question is: Do we indeed advise not to use --mtime=0 for source
> tarballs?  And if so, why is that?

HP-UX 'make' treats mtime 0 as a missing file, and POSIX encourage it:

https://lists.gnu.org/archive/html/bug-gnulib/2024-12/msg00209.html
https://lists.gnu.org/archive/html/bug-gnulib/2024-12/msg00227.html

If you want to depend on GNU make behaviour, all is good.

I think the bigger concern is make-based dependency build tracking of
generated files inside the tarball, for 'make dist' tarballs:

https://lists.gnu.org/archive/html/bug-gnulib/2024-12/msg00199.html
https://mail.gnu.org/archive/html/bug-gnulib/2025-02/msg00166.html
https://lists.gnu.org/archive/html/bug-gnulib/2024-12/msg00182.html

I think these are weak arguments, and I suggest we experiment with
--mtime=0 to see if anything breaks that cannot be fixed.

Including generated files inside a tarball is a bad idea.  Use
git-archive tarballs, and only put source code files in git.  However,
we will have to live with 'make dist' tarballs for a long time, and
sometimes vendoring some external files is reasonable to avoid really
complicated build dependencies.  So maybe Bruno's vc-mtime can be a
solution here, but it is quite complex.

/Simon
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