workflows/check-by-name: Move tool fetching into script

This part of the CI can also be reproduced locally

1 files changed, 45 insertions, 0 deletions

diff --git a/pkgs/test/nixpkgs-check-by-name/scripts/fetch-tool.sh b/pkgs/test/nixpkgs-check-by-name/scripts/fetch-tool.sh
new file mode 100755
index 0000000000000..fc4df11e747e6
--- /dev/null
+++ b/pkgs/test/nixpkgs-check-by-name/scripts/fetch-tool.sh
@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+# Fetches the prebuilt nixpkgs-check-by-name to use from
+# the NixOS channel corresponding to the given base branch
+
+set -euo pipefail
+
+if (( $# < 2 )); then
+    echo >&2 "Usage: $0 BASE_BRANCH OUTPUT_PATH"
+    echo >&2 "BASE_BRANCH: The base branch to use, e.g. master or release-23.11"
+    echo >&2 "OUTPUT_PATH: The output symlink path for the tool"
+    exit 1
+fi
+baseBranch=$1
+output=$2
+
+echo >&2 -n "Determining the channel to use for PR base branch $baseBranch.. "
+if [[ "$baseBranch" =~ ^(release|staging|staging-next)-([0-9][0-9]\.[0-9][0-9])$ ]]; then
+  # Use the release channel for all PRs to release-XX.YY, staging-XX.YY and staging-next-XX.YY
+  preferredChannel=nixos-${BASH_REMATCH[2]}
+else
+  # Use the nixos-unstable channel for all other PRs
+  preferredChannel=nixos-unstable
+fi
+
+# Check that the channel exists. It doesn't exist for fresh release branches
+if curl -fSs "https://channels.nixos.org/$preferredChannel"; then
+    channel=$preferredChannel
+    echo >&2 "$channel"
+else
+    # Fall back to nixos-unstable, makes sense for fresh release branches
+    channel=nixos-unstable
+    echo >&2 -e "\e[33mWarning: Preferred channel $preferredChannel could not be fetched, using fallback: $channel\e[0m"
+fi
+
+echo >&2 -n "Fetching latest version of channel $channel.. "
+# This is probably the easiest way to get Nix to output the path to a downloaded channel!
+nixpkgs=$(nix-instantiate --find-file nixpkgs -I nixpkgs=channel:"$channel")
+echo >&2 "$nixpkgs"
+
+# This file only exists in channels
+echo >&2 -e "Git revision of channel $channel is \e[34m$(<"$nixpkgs/.git-revision")\e[0m"
+
+echo >&2 -n "Fetching the prebuilt version of nixpkgs-check-by-name.. "
+nix-build -o "$output" "$nixpkgs" -A tests.nixpkgs-check-by-name -j 0 >/dev/null
+realpath >&2 "$output"