From ff2f85641a6568c550e50a76b5fb81fa1a3ee51d Mon Sep 17 00:00:00 2001
From: Mihai Fufezan <mihai@fufexan.net>
Date: Fri, 20 Jun 2025 00:50:46 +0300
Subject: [PATCH] CI/Nix: add cache-nix-action

Use nixbuild/nix-quick-install-action which pairs well with
nix-community/cache-nix-action.

Should help with build times by reducing the number of packages needing
to be re-downloaded on each run.

Parameters are taken from https://github.com/nix-community/cache-nix-action
and may be tweaked later.
---
 .github/workflows/nix-build.yml         | 30 +++++++++++++++++++++++-
 .github/workflows/nix-update-inputs.yml | 31 ++++++++++++++++++++++++-
 2 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/nix-build.yml b/.github/workflows/nix-build.yml
index 5b2e81cfd..55ac485ef 100644
--- a/.github/workflows/nix-build.yml
+++ b/.github/workflows/nix-build.yml
@@ -18,7 +18,35 @@ jobs:
 
     runs-on: ubuntu-latest
     steps:
-      - uses: DeterminateSystems/nix-installer-action@main
+      - name: Install Nix
+        uses: nixbuild/nix-quick-install-action@v31
+        with:
+          nix_conf: |
+            keep-env-derivations = true
+            keep-outputs = true
+
+      - name: Restore and save Nix store
+        uses: nix-community/cache-nix-action@v6
+        with:
+          # restore and save a cache using this key
+          primary-key: nix-${{ runner.os }}-${{ hashFiles('**/*.nix', '**/flake.lock') }}
+          # if there's no cache hit, restore a cache by this prefix
+          restore-prefixes-first-match: nix-${{ runner.os }}-
+          # collect garbage until the Nix store size (in bytes) is at most this number
+          # before trying to save a new cache
+          # 1G = 1073741824
+          gc-max-store-size-linux: 1G
+          # do purge caches
+          purge: true
+          # purge all versions of the cache
+          purge-prefixes: nix-${{ runner.os }}-
+          # created more than this number of seconds ago
+          purge-created: 0
+          # or, last accessed more than this number of seconds ago
+          # relative to the start of the `Post Restore and save Nix store` phase
+          purge-last-accessed: 0
+          # except any version with the key that is the same as the `primary-key`
+          purge-primary-key: never
 
       - uses: cachix/cachix-action@v15
         with:
diff --git a/.github/workflows/nix-update-inputs.yml b/.github/workflows/nix-update-inputs.yml
index c9a094a26..c83e98801 100644
--- a/.github/workflows/nix-update-inputs.yml
+++ b/.github/workflows/nix-update-inputs.yml
@@ -17,7 +17,36 @@ jobs:
         with:
           token: ${{ secrets.PAT }}
 
-      - uses: DeterminateSystems/nix-installer-action@main
+      - name: Install Nix
+        uses: nixbuild/nix-quick-install-action@v31
+        with:
+          nix_conf: |
+            keep-env-derivations = true
+            keep-outputs = true
+
+      - name: Restore and save Nix store
+        uses: nix-community/cache-nix-action@v6
+        with:
+          # restore and save a cache using this key
+          primary-key: nix-${{ runner.os }}-${{ hashFiles('**/*.nix', '**/flake.lock') }}
+          # if there's no cache hit, restore a cache by this prefix
+          restore-prefixes-first-match: nix-${{ runner.os }}-
+          # collect garbage until the Nix store size (in bytes) is at most this number
+          # before trying to save a new cache
+          # 1G = 1073741824
+          gc-max-store-size-linux: 1G
+          # do purge caches
+          purge: true
+          # purge all versions of the cache
+          purge-prefixes: nix-${{ runner.os }}-
+          # created more than this number of seconds ago
+          purge-created: 0
+          # or, last accessed more than this number of seconds ago
+          # relative to the start of the `Post Restore and save Nix store` phase
+          purge-last-accessed: 0
+          # except any version with the key that is the same as the `primary-key`
+          purge-primary-key: never
+
       - name: Update inputs
         run: nix/update-inputs.sh