rr: 5.3.0 +> 9ff37581 add rr-unstable until a new rr release is made

pkgs/development/tools/analysis/rr/unstable.nix

@@ -0,0 +1,23 @@
+# This is a temporary copy of the default.nix in this folder, with the version updated to the current tip of rr's master branch.
+# This exists because rr has not had a release in a long time, but there have been a lot of improvements including UX.
+# Some of the UX improvements help prevent foot shooting.
+# Upstream has stated that it should be fine to use master.
+# This file, and its attribute in all-packages, can be removed once rr makes a release.
+# For further information, please see https://github.com/NixOS/nixpkgs/issues/99535 "Improve support for the rr debugger in nixos containers"
+
+{ callPackage, fetchFromGitHub }:
+
+let
+  rr = callPackage ./. {};
+in
+
+  rr.overrideAttrs (old: {
+    version = "unstable-2020-10-04";
+
+    src = fetchFromGitHub {
+      owner = "mozilla";
+      repo = "rr";
+      rev = "9ff375813a740a0a6ebcdfcebc58bd61ab68c667";
+      sha256 = "0raifs6cg5ckpi2445inhy3hfhp4p89s1lkx9z17mcc2g1c1phf5";
+    };
+  })

pkgs/top-level/all-packages.nix

@@ -11523,6 +11523,7 @@ in
   rolespec = callPackage ../development/tools/misc/rolespec { };
 
   rr = callPackage ../development/tools/analysis/rr { };
+  rr-unstable = callPackage ../development/tools/analysis/rr/unstable.nix { }; # This is a temporary attribute, please see the corresponding file for details.
 
   samurai = callPackage ../development/tools/build-managers/samurai { };