This reverts commit 65a333600d.
This wasn't tested for correctness with something like fodwatch [0],
and should not have been (self-)merged so quickly, especially without
further review.
It also resulted in the breakage of at least one package [1] (and that's
the one we know of and was caught).
A few packages that were updated in between this commit and this revert
were not reverted back to using `rev`, but other than that, this is a
1:1 revert.
[0]: https://codeberg.org/raphaelr/fodwatch
[1]: https://github.com/NixOS/nixpkgs/pull/396904 / 758551e458
a19cd4ffb1