@orivej: The hash of this patch seems to have changed even though it was already using fetchpatch and the commit hash hasn't changed. Any clues as to why?

That hash was generated with patchutils 0.3.4 which existed between #24825 and 814772e

Thank you! How do you systematically find broken hashes?

@orivej: Hydra caches source files very aggressively, so once a source file gets successfully downloaded, Hydra doesn't notice anymore if the source file has changed upstream.

However, I use my own Hydra server to compile all of the packages that I use on all of my machines, so I tend to catch these kind of issues sometimes, usually either because a) by the time my Hydra server gets to download and check the hash of a source file, it has changed upstream for some reason, or b) someone has updated a package but forgot to change the source hash.

Hydra doesn't care that someone changes the URL/version of a source file - if the hash remains the same, Hydra assumes that the source file hasn't changed. But when I compile that package on my own Hydra server, I may notice the hash doesn't match because unlike NixOS's Hydra server, I may not have the previous source file cached locally, which means my Hydra server has to actually download it and check the hash.

This can actually be a bit of an annoyance for me, but fortunately it's usually easily fixed. Sometimes patches and/or source files do disappear from upstream, which can make my life a bit harder.

@orivej @wizeman this actually seems to have produced a broken hash. See #34046 for my confusion on the issue. I'll probably revert it, since any attempt to --check that fetchpatch call now fails.

Maybe another change in patchutils changed this hash again?

Edit: no, not that. We're still on the reverted 0.3.3 version.

It seems to be healthy in master again (maybe due to @Ericson2314's recent change to fetchpatch?), but is still broken in 17.09. I'm confused.

Edit: not that either. No idea what's wrong, but I'm going to fix the hash in 17.09 and move on.

Never mind, it turns out this just needed backporting to 17.09. Mystery solved 😦