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

5.20151116+gitg5416a1a-1~ndall+1

### Please provide any additional information below.

[[!format sh """
    "backend usage": [
        [
            "MD5E",
            2
        ],
        [
            "SHA256E",
            2
        ]
    ],
"""]]

instead of more logical

[[!format sh """

    "backend usage": {
         "MD5E": 2,
         "SHA256E": 2
    }
"""]]

also it seems it just doubles them since I have only 2 files, 1 for each backend (as reported also by info "local annex keys": 2). 

[[!meta author=yoh]]
[[!tag projects/datalad]]

> [[fixed|done]] --[[Joey]]
