Allow git-annex to recognise repo as an annex-capable remote

Its own test fails like this:

```
$ git annex init --debug
...
[2018-09-26 11:53:56.198970849] Request {
host = "web.gin.g-node.org"
port = 443
secure = True
requestHeaders = [("Range","bytes=0-"),("Accept-Encoding","identity")]
path = "/INT/multielectrode_grasp/config"
queryString = ""
method = "GET"
proxy = Nothing
rawBody = False
redirectCount = 10
responseTimeout = ResponseTimeoutDefault
requestVersion = HTTP/1.1
}

download failed: Not Found

```