Project files and folders are not documented

Hi, when I run art create to start a new project, the following files are created (Artanis 0.6):

musicbox/
|-- ENTRY
|-- README
|-- app
|   |-- controllers
|   |-- models
|   |-- protocols
|   `-- views
|-- conf
|   |-- README
|   `-- artanis.conf
|-- db
|   |-- migration
|   `-- sm
|-- lib
|-- log
|-- prv
|-- pub
|   |-- css
|   |-- img
|   |   `-- upload
|   `-- js
|-- sys
|   |-- i18n
|   `-- pages
|-- test
|   |-- benchmark
|   |   `-- README
|   |-- functional
|   `-- unit
`-- tmp
    `-- cache
        |-- README
        |-- migration
        `-- route.cache

I can understand the purpose of some files and folders, but I'm not sure about the purpose of some others. Some folders contain READMEs, but they are empty.

For example, I'd like to know if the following directories should be placed in version control or not:

lib
log
prv
tmp

But it is not obvious because, for instance, if I delete tmp, running art work fails as follows:

Regenerating route cache ...
Backtrace:
In ice-9/boot-9.scm:
  1752:10 12 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
          11 (apply-smob/0 #<thunk 7f1f6c6c1300>)
In ice-9/boot-9.scm:
    724:2 10 (call-with-prompt _ _ #<procedure default-prompt-handle?>)
In ice-9/eval.scm:
    619:8  9 (_ #(#(#<directory (guile-user) 7f1f6c6c4c80>)))
In /gnu/store/3h9r7y4vy2b6ychskhn7q0kbl3zawhvv-artanis-0.6/bin/.art-real:
    48:12  8 (_ _ _)
In artanis/commands/work.scm:
    145:9  7 (work . _)
In artanis/artanis.scm:
    338:3  6 (run #:host _ #:port _ #:debug _ #:use-db? _ #:db-proto ?)
In unknown file:
           5 (run-hook #<hook 0 7f1f68df2750 init-work>)
In artanis/commands/work.scm:
    128:2  4 (init-work)
In artanis/utils.scm:
    906:4  3 (dump-route-from-cache)
    872:4  2 (cache-this-route! #f #f)
In ice-9/ports.scm:
   467:11  1 (call-with-output-file "/home/user/bogus/?" ?)
In unknown file:
           0 (open-file "/home/user/bogus/?" ?)

ERROR: In procedure open-file:
In procedure open-file: No such file or directory: "/home/user/bogus/tmp/cache/route.cache"

(project path redacted for privacy)

Thanks in advance :)