Merge branch 'add-runit-to-logs-docs' into 'master'

Docs: add runit log explanation to logs.md

See merge request gitlab-org/gitlab!27163

doc/administration/logs.md

@@ -434,6 +434,10 @@ I, [2015-02-13T06:17:00.679433 #9291]  INFO -- : Moving existing hooks directory
 
 User clone/fetch activity using SSH transport appears in this log as `executing git command <gitaly-upload-pack...`.
 
+## `current`
+
+This file lives in `/var/log/gitlab/gitaly/current` and is produced by [runit](http://smarden.org/runit/). `runit` is packaged with Omnibus and a brief explanation of its purpose is available [in the omnibus documentation](https://docs.gitlab.com/omnibus/architecture/#runit). [Log files are rotated](http://smarden.org/runit/svlogd.8.html), renamed in unix timestamp format and `gzip`-compressed (e.g. `@1584057562.s`).
+
 ## `unicorn_stderr.log`
 
 This file lives in `/var/log/gitlab/unicorn/unicorn_stderr.log` for