feat: combine stdout and stderr, pipe to tee
Related to https://github.com/tailscale/github-action/issues/140
Ideally it would be nice to set a variable and not send the logs to a file at all, but instead just let them come up in the job logs... this is a good start when it comes to debugging though, having this same problem around seeing errors logs right now.
Apologies, the action is now implemented in JavaScript. If you'd be willing to resubmit your PR, we will review it.
Writing to a log file makes sense here, since tailscaled runs in the background and outputting its logs to the job's console would interfere with the interactive commands that get run after tailscaled starts.
Please set this up so that it only captures the output if debug logging is enabled. You can check for that with core.isDebug().