Re: Generated patches change over time

[ludo@gnu.org (Ludovic Courtès)]

Hello Mark,

Mark H Weaver <mhw@netris.org> skribis:

> ludo@gnu.org (Ludovic Courtès) writes:

[...]

>> Lesson learned: we should not rely at all on generated patches because
>> they are bound to change frequently (version string at the end, length
>> of commit hash prefixes, etc.)  It’s probably worse than tarballs
>> generated by Git hosting services.
>
> I guess the length of the commit hashes probably won't change very
> often, so the version number is the most pressing issue here.

Overall though such patches may typically change several times a year.

> I wonder if it would be worth adding a special 'origin' type that
> removes the version number from the end of git patches.

As I replied to Maxim, this is not really possible.

>> So we should probably work towards using local copies of patches, unless
>> we find that the generated patches do not include any variable bits.
>
> It might still be best to work towards using local copies of patches,
> although in the case of IceCat the set of patches is often quite large.
>
> Another issue to consider is that the use of local copies of patches
> involves putting more trust in contributors, in practice, or at least it
> seems so to me.  When someone adds a non-obvious patch from upstream as
> a local file, it leads me to want to check to make sure it hasn't been
> modified from the upstream version, whereas if the package recipe
> fetches a patch from a URL that is clearly from the upstream git
> repository, it's somewhat more transparent what's going on.

Yeah I agree with this.  Another concern is unbounded growth of the Git
repo.

OTOH a patch that changes over time becomes non auditable: you’ll notice
it has changed, and maybe that’s because of a benign change like those
discussed above, but maybe it’s something else; if you can’t retrieve or
reproduce the original patch, you can’t tell what the difference is.

So I don’t have a good solution, but I think we should avoid upstream
patches when we know they are generated in a non-reproducible fashion.

Thanks,
Ludo’.