Describe the bug

The point of fetchpatch and fetchpatch2 is to prevent changes in API-generated patches that don't affect the patched tree from affecting the hash of the fetched patch.

GitHub dynamically chooses the length of abbreviated commit hashes in a number of places, and (I guess) also in the generated patches.

Some time around August, a commit hash in the following patch changed from 5d7ffe2d91910 to 5d7ffe2d91910a.

/* was: */ (pkgs.fetchpatch2 { url = "https://github.com/NixOS/nixpkgs/commit/eeff6c493373d3fff11421b55309fab6a1d4ec7d.diff"; sha256 = "sha256-Sqt1FQG+0j9dJMtZiBX+dK3UW5SH5Gtg8zVFTs0F23s="; })
/* now: */ (pkgs.fetchpatch2 { url = "https://github.com/NixOS/nixpkgs/commit/eeff6c493373d3fff11421b55309fab6a1d4ec7d.diff"; sha256 = "sha256-Z5vENYxMNBmTUuhzug9Kgi7/21J1X6d7BxqovyOv9fg="; })

diff --git a/pkgs/os-specific/linux/systemd/default.nix b/pkgs/os-specific/linux/systemd/default.nix
index 5d7ffe2d91910..14d5e29c372a88 100644
--- a/pkgs/os-specific/linux/systemd/default.nix
+++ b/pkgs/os-specific/linux/systemd/default.nix
@@ -178,6 +178,13 @@
     # need (AFAICT).
     # See https://github.com/systemd/systemd/pull/20479 for upstream discussion.
     ./0019-core-handle-lookup-paths-being-symlinks.patch
+
+    # fixes reproducability of dbus xml files
+    # Should no longer be necessary with v251.
+    (fetchpatch {
+      url = "https://github.com/systemd/systemd/pull/22174.patch";
+      sha256 = "sha256-RVhxUEUiISgRlIP/AhU+w1VHfDQw2W16cFl2TXXyxno=";
+    })
   ] ++ lib.optional stdenv.hostPlatform.isMusl (
     let
       oe-core = fetchzip {

I still had that file in a local store. The new output is identical, except it uses 5d7ffe2d91910a as the commit hash.

Steps To Reproduce

That's difficult, since GitHub does not provide the old patch file anymore.
I assume the only difference in the patch files was exactly that hash.

Expected behavior

Stable output by fetchpatch and fetchpatch2.

fetchpatch2 is fairly new and hardly used in nixpkgs. Maybe it should be updated to normalize/strip the hashes? Or we get a fetchpatch3 ...

Notify maintainers

@Artturin