bazzite/system_files/deck/shared/usr/libexec/os-branch-select

#!/bin/bash
set -e

if [[ $# -eq 1 ]]; then
  case "$1" in
    "-c")
      if [[ -f /var/ublue-update/branch ]]; then
        branch=$(cat /var/ublue-update/branch)
      else
        branch=$(cut -d ":" -f4 <<< "$(rpm-ostree status | grep -m 1 'bazzite')")
      fi

      case "$branch" in
        "latest")
          echo rel
          exit 0
          ;;
        "testing")
          echo rc
          exit 0
          ;;
        "unstable")
          echo main
          exit 0
          ;;
        *)
          # This can happen on CI builds or when downgrading from a newer build that knows of more branches.  The update
          # path should decide how to handle it.
          echo >&2 "Warning: Unrecognized currently selected branch name '$branch', updates may not succeed."
          echo "$branch"
          exit 0
          ;;
      esac
      ;;
    "-l")
      echo rel
      echo rc
      echo beta
      echo bc
      echo main
      exit 0
      ;;
    "rel" | "latest")
      /usr/bin/pkexec /usr/libexec/ublue-update-rebase "latest"
      exit 0
      ;;
    "rc" | "beta" | "testing")
      /usr/bin/pkexec /usr/libexec/ublue-update-rebase "testing"
      exit 0
      ;;
    "bc" | "main" | "unstable")
      echo "The unstable branch has a high risk of breaking."
      echo "Do NOT use it unless you know what you are doing."
      /usr/bin/pkexec /usr/libexec/ublue-update-rebase "unstable"
      exit 0
      ;;
  esac
fi

echo "Usage: steamos-select-branch <latest|testing|unstable>" 1>&2