.github: Try reinstalling homebrew

.github/workflows/ci.yaml

@@ -5,7 +5,7 @@ on:
   pull_request:
 
 jobs:
-  check:
+  check-migrate:
     runs-on: macos-13
     steps:
       - uses: actions/checkout@v3
@@ -43,3 +43,36 @@ jobs:
       #- name: Migrate to fully-declarative tap management
       #  run: |
       #    false
+
+  check-non-standard-prefix:
+    runs-on: macos-13
+    steps:
+      - uses: actions/checkout@v3
+      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+
+      - name: Set up /run for nix-darwin
+        run: |
+          printf 'run\tprivate/var/run\n' | sudo tee -a /etc/synthetic.conf
+          sudo /System/Library/Filesystems/apfs.fs/Contents/Resources/apfs.util -t || true
+
+      - name: Install Homebrew
+        run: |
+          sudo rm /etc/bashrc
+          ./ci/activate-example.sh non-standard-prefix
+
+      - name: Check that we can install packages
+        run: |
+          brew_path=$(type -P brew)
+          if [[ "${brew_path}" != "/run/current-system/sw/bin/brew" ]]; then
+            >&2 echo "brew is ${brew_path}, not /run/current-system/sw/bin/brew"
+            exit 1
+          fi
+
+          brew_prefix=$(brew --prefix)
+          if [[ "${brew_prefix}" != "/opt/nix-homebrew" ]]; then
+            >&2 echo "brew prefix is ${brew_prefix}, not /opt/nix-homebrew"
+            exit 1
+          fi
+
+          brew install gmp

ci/default.nix

@@ -22,4 +22,5 @@ let
   };
 in {
   migrate = makeProfile "migrate";
+  non-standard-prefix = makeProfile "non-standard-prefix";
 }

ci/example.json

@@ -1 +0,0 @@
-migrate

ci/step.json

@@ -1 +0,0 @@
-"migrate"

examples/non-standard-prefix.nix

@@ -0,0 +1,19 @@
+# Use a non-standard prefix
+
+{ pkgs, ... }:
+{
+  nix-homebrew = {
+    enable = true;
+    prefixes = {
+      "/usr/local".enable = true;
+      "/opt/homebrew".enable = true;
+      "/opt/nix-homebrew" = {
+        enable = true;
+        library = "/opt/nix-homebrew/Library";
+      };
+    };
+    user = "yourname";
+    defaultIntelPrefix = "/opt/nix-homebrew";
+    defaultArm64Prefix = "/opt/nix-homebrew";
+  };
+}