Update nix flake inputs structure and add rv-nix-tools to dependency update workflow (#1207)

This pull request adapts the nix flake inputs structure regarding
`nixpkgs` and `rv-nix-tools`. In particular, `nixpkgs` is now specified
for inputs and transitive inputs by following an explicitly specified
revision of `rv-nix-tools`. More thorough reasoning for this change is
outlined in documentation added by this PR
runtimeverification/rv-nix-tools#14. This change is done to make
`nixpkgs` properly updatable by CI.

In addition, this pull requests adapts the `update-deps.yml` workflow to
also update `rv-nix-tools` that is used to implicitly specify the
revision of `nixpkgs`.

Author: juliankuners

.github/workflows/update-deps.yml

@@ -3,6 +3,7 @@ on:
   push:
     branches:
       - '_update-deps/runtimeverification/scala-kore'
+      - '_update-deps/runtimeverification/rv-nix-tools'
   workflow_dispatch:
 # Stop in progress workflows on the same branch and same workflow to use latest committed code
 concurrency:
@@ -25,8 +26,23 @@ jobs:
           git config user.name devops
           git config user.email [email protected]
 
+      - name: 'Install Nix'
+        uses: cachix/install-nix-action@v22
+        with:
+          install_url: https://releases.nixos.org/nix/nix-2.13.3/install
+          extra_nix_config: |
+            substituters = http://cache.nixos.org https://hydra.iohk.io
+            trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=
+
       - name: 'Update scala-kore release tag'
         run: ./scripts/update-scala-kore.sh
 
+      - name: 'Update Nix flake inputs'
+        run: |
+          RV_NIX_TOOLS_VERSION=$(cat deps/rv-nix-tools)
+          sed -i 's!    rv-nix-tools.url = "github:runtimeverification/rv-nix-tools/[a-z0-9\.]*"!    rv-nix-tools.url = "github:runtimeverification/rv-nix-tools/'"${RV_NIX_TOOLS_VERSION}"'"!' flake.nix
+          nix flake update
+          git add flake.nix flake.lock && git commit -m 'flake.{nix,lock}: update Nix derivations' || true
+
       - name: 'Push updates'
         run: git push

deps/rv-nix-tools

@@ -0,0 +1 @@
+854d4f05ea78547d46e807b414faad64cea10ae4

flake.lock

@@ -2,9 +2,10 @@
   description = "K Kore Language LLVM Backend";
 
   inputs = {
+    rv-nix-tools.url = "github:runtimeverification/rv-nix-tools/854d4f05ea78547d46e807b414faad64cea10ae4";
+    nixpkgs.follows = "rv-nix-tools/nixpkgs";
+
     utils.url = "github:numtide/flake-utils";
-    rv-utils.url = "github:runtimeverification/rv-nix-tools";
-    nixpkgs.follows = "rv-utils/nixpkgs";
 
     fmt-src.url =
       "github:fmtlib/fmt/9.1.0";