### Please describe the problem.
Just a small patch to Tahoe.hs which fixes "initremote repo
type=thaoe" when using the latest tahoe-lafs release available for
download.

I'm trying to add an attachment here but the UI says "prohibited by 
allowed_attachments (user is not an admin)" so please have a look also 
here: <https://github.com/joeyh/git-annex/pull/21>

### What steps will reproduce the problem?

1. Install latest tahoe-lafs
2. run "TAHOE_FURL=... git annex initremote repo type=tahoe"

### What version of git-annex are you using? On what operating system?

OS: Debian Sid updated to latest packages
git-annex: version 5.20140306 

> Thanks, I've fixed this. [[done]] --[[Joey]]

### Please provide any additional information below.

I would like to add few things if i'm able (it's my first time for
haskell, and I'm a bit lost as now):

1. add an optional parameter or envvar for a root dir cap and switch
from storing anonymous files to saving a tree of dirs and files
(much like the webdav back-end) so that i can later renew the
leases on the files to prevent tahoe's garbage collection process
expiration (for details see
<https://tahoe-lafs.org/trac/tahoe-lafs/browser/docs/garbage-collection.rst#client-side-renewal>)

The poor man way to that without touching git-annex is to in some
way collect the caps of the files from annex metadatas and to link
them to a directory, which where i can then run "tahoe deep-check
--add-lease" on;

> When I talked this over with Zooko before, he 
> thought it was better for git-annex to not use tahoe's directories,
> which is why it doesn't. See [[todo/tahoe_lfs_for_reals]].
> 
> This is the first I have heard about tahoe garbage collection. 
> It sounds like it's an optional process.
> 
> It would certainly be possible to pull the caps for files out of
> git-annex's remote state log.
> --[[Joey]]

2. add convergence as an optional parameter. As of now many of the
files that i'm willing to manage with git-annex are already on my
grid, mostly because i've used tahoe's backup command to upload
them in the past. By using the same convergence value that i've
already setup on my other tahoe client installation i would be able
to save much time and space by avoiding duplicates.

Do you have any good pointers to pieces code of git-annex that i can
read and hack to try to implement this or any other suggestion?

> It was not documented, but you can already pass
> `shared-convergence-secret=xxx` to `initremote`.
> I have documented it. --[[Joey]]
