Merge pull request #269094 from NixOS/backport-269092-to-release-23.11

      - uses: cachix/install-nix-action@v23

      - name: Determining channel to use for dependencies

        run: |

          echo "Determining which channel to use for PR base branch $GITHUB_BASE_REF"

          echo "Determining the preferred channel to use for PR base branch $GITHUB_BASE_REF"

          if [[ "$GITHUB_BASE_REF" =~ ^(release|staging|staging-next)-([0-9][0-9]\.[0-9][0-9])$ ]]; then

              # Use the release channel for all PRs to release-XX.YY, staging-XX.YY and staging-next-XX.YY

              channel=nixos-${BASH_REMATCH[2]}

              echo "PR is for a release branch, using release channel $channel"

              echo "PR is for a release branch, preferred channel is $channel"

          else

              # Use the nixos-unstable channel for all other PRs

              channel=nixos-unstable

              echo "PR is for a non-release branch, using unstable channel $channel"

              echo "PR is for a non-release branch, preferred channel is $channel"

          fi

          # Check that the channel exists. It doesn't exist for fresh release branches

          if ! curl -fSs "https://channels.nixos.org/$channel"; then

            # Fall back to nixos-unstable, makes sense for fresh release branches

            echo "Preferred channel $channel could not be fetched, falling back to nixos-unstable"

            channel=nixos-unstable

          fi

          echo "channel=$channel" >> "$GITHUB_ENV"

      - name: Fetching latest version of channel