feat: add log.job.dir (#1165)

`log.job.dir` makes the runner write a copy of every task's log to that directory, as `<start time>-task-<id>.log`: the rows exactly as Gitea received them, with the same masking and the job's result on the last line. Off by default, and what Gitea shows does not change.

`log.job.retention` (default `168h`) and `log.job.max_size` (default `1GB`) bound the directory. Documented in the README.

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Co-authored-by: silverwind <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1165
Reviewed-by: silverwind <[email protected]>

README.md

@@ -386,6 +386,12 @@ Both hooks are synchronous and block the job while they run. Either one exiting
 
 See **[docs/job-hooks.md](docs/job-hooks.md)** for the execution order, environment, and platform notes.
 
+#### Local job logs (`log.job.dir`)
+
+Set `log.job.dir` to a path and the runner writes a copy of every task's log there as `<start time>-task-<id>.log`: the rows exactly as Gitea received them, with the same secrets masked and the job's result on the last line. Off by default, and what Gitea shows does not change.
+
+`log.job.retention` (default `168h`) is how long a log is kept, expired ones being deleted as new tasks start, and `log.job.max_size` (default `1GB`) caps one log. Keep `retention` above `runner.timeout` so a long job cannot outlive its own log, and prefer local disk, the file is written while the job runs. Only the runner's own user can read it.
+
 ### Example Deployments
 
 Check out the [examples](examples) directory for sample deployment types.