time-machine broken from 2019-04-07 to 2019-05-04

[zimoun]

Dear,

This bug [1] shows that 1100+ commits are broken for the time machine, i.e,,

  guix time-machine --commit=<xxx> -- <anything>

will fail.

The reason is the upstream in-place update of the SHA (bad practise!
bouhbouh!! :-)).

Upstream has released the version 2.4.0 of harfbuzz with the hash
1mpah6kwqid1kxsj4rwqsniivqbrx231j65v51yncx6s0dch0dch then changed it
[2] to  0vrkvdlmihdg62a4c6h5kx27khc33xmb95l50zgnwnavvpwyyw5l.

The version 2.4.0 has been introduced in Guix with the commit
2da9b81837fd1e6f08a10952784d3358be982855 using the first hash. Then
the commit  a8bb8fccd82a10a46f127b2235675b4f6cbaaf98 fixes the
upstream mess.

But, it means that all the commits between these two ones cannot be
built by Guix because a SHA mismatch error is raised.


Is the diagnostic correct?


What should be the fix?
Because it is annoying to be dependent of upstream bad practise.

Well, is it fixable?

(The initial tarball could recreated by one of us and then pushed to
SWH, but I am not convinced it is enough... because the time-machine
should check the availability of the source etc. which adds a lot of
complexity.)


What do you think?


All the best,
simon


[1] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=39575
[2] https://github.com/harfbuzz/harfbuzz/issues/1641.