From d73485322345297b321fcfd02c618b88c1f2d85e Mon Sep 17 00:00:00 2001
From: technofab <admin@technofab.de>
Date: Sat, 22 Mar 2025 21:50:33 +0100
Subject: [PATCH] chore(scripts): improve cache strategy handling, see #21

---
 scripts/finalize_nix_ci.sh  |  4 ++++
 scripts/setup_nix_ci.sh     |  5 +++++
 templates/nix-gitlab-ci.yml | 11 ++++++++---
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/scripts/finalize_nix_ci.sh b/scripts/finalize_nix_ci.sh
index e1200c2..698b81f 100644
--- a/scripts/finalize_nix_ci.sh
+++ b/scripts/finalize_nix_ci.sh
@@ -6,6 +6,10 @@ echo -e "\\e[0Ksection_start:`date +%s`:finalize_nix_ci[collapsed=true]\\r\\e[0K
     /tmp/nix-store-before /tmp/nix-store-after)
   COUNT=$(${pkgs.busybox}/bin/wc -l <<<"$NEW_PATHS")
 
+  if [[ "$NIX_CI_CACHE_STRATEGY" == "auto" ]]; then
+    export NIX_CI_CACHE_STRATEGY="${NIX_CI_RUNNER_CACHE_STRATEGY:-${NIX_CI_DEFAULT_CACHE_STRATEGY:-none}}";
+  fi
+
   if [ -z "$NIX_CI_DISABLE_CACHE" ]; then
     echo -e "\\e[0Ksection_start:`date +%s`:cache_push[collapsed=true]\\r\\e[0KPushing $COUNT new store paths to cache ($NIX_CI_CACHE_STRATEGY)"
       echo $NEW_PATHS | {
diff --git a/scripts/setup_nix_ci.sh b/scripts/setup_nix_ci.sh
index d91e17d..1f2af66 100644
--- a/scripts/setup_nix_ci.sh
+++ b/scripts/setup_nix_ci.sh
@@ -1,6 +1,11 @@
 echo -e "\\e[0Ksection_start:`date +%s`:nix_setup[collapsed=true]\\r\\e[0KSetting up Nix CI"
   nix path-info --all > /tmp/nix-store-before
 
+  if [[ "$NIX_CI_CACHE_STRATEGY" == "auto" ]]; then
+    export NIX_CI_CACHE_STRATEGY="${NIX_CI_RUNNER_CACHE_STRATEGY:-${NIX_CI_DEFAULT_CACHE_STRATEGY:-none}}";
+    echo "NIX_CI_CACHE_STRATEGY was set to auto, selected '$NIX_CI_CACHE_STRATEGY' for this job"
+  fi
+
   if [ -z "$NIX_CI_DISABLE_CACHE" ]; then
     echo -e "\\e[0Ksection_start:`date +%s`:cache_setup[collapsed=true]\\r\\e[0KConfiguring cache ($NIX_CI_CACHE_STRATEGY)"
       case "$NIX_CI_CACHE_STRATEGY" in
diff --git a/templates/nix-gitlab-ci.yml b/templates/nix-gitlab-ci.yml
index b00ac79..cc87788 100644
--- a/templates/nix-gitlab-ci.yml
+++ b/templates/nix-gitlab-ci.yml
@@ -3,9 +3,14 @@ spec:
     cache_strategy:
       type: string
       description: |
-        (empty for auto) | none | runner | cachix | attic
-        Sets the default strategy and will be overridden by $NIX_CI_CACHE_STRATEGY
-      default: "none"
+        auto (default) | none | runner | cachix | attic
+        Sets the default caching strategy. 
+        - "auto": dynamically selects the best strategy for every job based on env variables
+        - "none": disables caching
+        - "runner", "cachix" & "attic": forces every job to use this strategy
+
+        Can be overridden by setting NIX_CI_CACHE_STRATEGY in the pipeline variables.
+      default: "auto"
     cache_files:
       type: array
       description: |