README: fix syntax

Test for act

.github/workflows/test.yml

@@ -109,3 +109,17 @@ jobs:
         nix_path: nixpkgs=channel:nixos-21.05
         install_url: https://releases.nixos.org/nix/nix-2.3.5/install
     - run: nix-build test.nix
+
+  act-support: 
+    strategy:
+        matrix:
+          os: [ubuntu-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@v2.4.0
+    - uses: actions/setup-go@v2.1.4
+      with:
+        go-version: '^1.16'
+    - run: go install github.com/nektos/act@master
+    - run: docker pull ghcr.io/catthehacker/ubuntu:js-20.04
+    - run: ~/go/bin/act -P ubuntu-latest=ghcr.io/catthehacker/ubuntu:js-20.04 push -j simple-build 

README.md

@@ -18,7 +18,7 @@ or [pin nixpkgs yourself](https://nix.dev/reference/pinning-nixpkgs.html)
 - Allows specifying extra Nix configration options via `extra_nix_config`
 - Allows specifying `$NIX_PATH` and channels via `nix_path`
 - Share `/nix/store` between builds using [cachix-action](https://github.com/cachix/cachix-action) for simple binary cache setup to speed up your builds and share binaries with your team
-- Enables `flakes` and `nix-command` experimental features by default (to disable, set ``experimental-features` via `extra_nix_config`) 
+- Enables `flakes` and `nix-command` experimental features by default (to disable, set ``experimental-features`` via ``extra_nix_config``) 
 
 ## Usage
 
@@ -33,8 +33,8 @@ jobs:
   tests:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2.3.4
+    - uses: actions/checkout@v2.4.0
-    - uses: cachix/install-nix-action@v14.1
+    - uses: cachix/install-nix-action@v15
       with:
         nix_path: nixpkgs=channel:nixos-unstable
     - run: nix-build
@@ -52,11 +52,9 @@ jobs:
   tests:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2.3.4
+    - uses: actions/checkout@v2.4.0
-    - uses: cachix/install-nix-action@v14.1
+    - uses: cachix/install-nix-action@v15
       with:
-        install_url: https://nixos-nix-install-tests.cachix.org/serve/vij683ly7sl95nnhb67bdjjfabclr85m/install
-        install_options: '--tarball-url-prefix https://nixos-nix-install-tests.cachix.org/serve'
         extra_nix_config: |
           access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
     - run: nix build

lib/install-nix.sh

@@ -6,9 +6,13 @@ if type -p nix &>/dev/null ; then
   exit
 fi
 
+# Create a temporary workdir
+workdir=$(mktemp -d)
+trap 'rm -rf "$workdir"' EXIT
+
 # Configure Nix
 add_config() {
-  echo "$1" | tee -a /tmp/nix.conf >/dev/null
+  echo "$1" | tee -a "$workdir/nix.conf" >/dev/null
 }
 # Set jobs to number of cores
 add_config "max-jobs = auto"
@@ -18,7 +22,7 @@ add_config "trusted-users = root $USER"
 if [[ $INPUT_EXTRA_NIX_CONFIG != "" ]]; then
   add_config "$INPUT_EXTRA_NIX_CONFIG"
 fi
-if [[ ! $INPUT_EXTRA_NIX_CONFIG =~ "experimental-features" ]]; then  
+if [[ ! $INPUT_EXTRA_NIX_CONFIG =~ "experimental-features" ]]; then
   add_config "experimental-features = nix-command flakes"
 fi
 
@@ -26,36 +30,43 @@ fi
 installer_options=(
   --no-channel-add
   --darwin-use-unencrypted-nix-store-volume
-  --nix-extra-conf-file /tmp/nix.conf
+  --nix-extra-conf-file "$workdir/nix.conf"
 )
 
 # only use the nix-daemon settings if on darwin (which get ignored) or systemd is supported
 if [[ $OSTYPE =~ darwin || -e /run/systemd/system ]]; then
   installer_options+=(
     --daemon
-    --daemon-user-count `python -c 'import multiprocessing as mp; print(mp.cpu_count() * 2)'`
+    --daemon-user-count "$(python -c 'import multiprocessing as mp; print(mp.cpu_count() * 2)')"
   )
 else
   # "fix" the following error when running nix*
   # error: the group 'nixbld' specified in 'build-users-group' does not exist
   add_config "build-users-group ="
+  mkdir -m 0755 /etc/nix
+  cp $workdir/nix.conf /etc/nix/nix.conf
 fi
 
 if [[ $INPUT_INSTALL_OPTIONS != "" ]]; then
-  IFS=' ' read -r -a extra_installer_options <<< $INPUT_INSTALL_OPTIONS
+  IFS=' ' read -r -a extra_installer_options <<< "$INPUT_INSTALL_OPTIONS"
   installer_options=("${extra_installer_options[@]}" "${installer_options[@]}")
 fi
 
-echo "installer options: ${installer_options[@]}"
+echo "installer options: ${installer_options[*]}"
 
 # There is --retry-on-errors, but only newer curl versions support that
-until curl -o /tmp/install -v --fail --retry 5 --retry-connrefused -L "${INPUT_INSTALL_URL:-https://nixos.org/nix/install}" 
+curl_retries=5
+while ! curl -o "$workdir/install" -v --fail -L "${INPUT_INSTALL_URL:-https://nixos.org/nix/install}"
 do
   sleep 1
+  ((curl_retries--))
+  if [[ $curl_retries -le 0 ]]; then
+    echo "curl retries failed" >&2
+    exit 1
+  fi
 done
 
-chmod +x /tmp/install
+sh "$workdir/install" "${installer_options[@]}"
-sh /tmp/install "${installer_options[@]}"
 
 if [[ $OSTYPE =~ darwin ]]; then
   # macOS needs certificates hints