Hello,

I have a repo alpha

```
florian@asaru ~/git-annex % tree
.
└── alpha
    ├── archive
    │   └── some_archived_file
    └── some_file
```

which is standard/client.

Another repo beta, cloned from alpha is also standard/client. ```git annex sync --content``` makes beta get all the content. Perfect!

Another repo delta, also cloned from alpha is:

```
% git annex wanted . && git annex group .
standard
archive backup
```
Manpage of git-annex-group says a repo could be in multiple groups.

I expect the groups to be combined. archive makes the other repos drop content in archive/ when it has reached this repo, backup to also retain deleted files.

But ```git annex sync --content``` gets no files:

```
florian@asaru ~/git-annex/delta (git)-[master] % git annex sync --content
commit  
Auf Branch master
Ihr Branch ist auf dem selben Stand wie 'origin/master'.
nichts zu committen, Arbeitsverzeichnis unverändert
ok
pull origin 
ok
```
```
florian@asaru ~/git-annex/delta (git)-[master] % git annex info          
repository mode: indirect
trusted repositories: 0
semitrusted repositories: 5
        00000000-0000-0000-0000-000000000001 -- web
        00000000-0000-0000-0000-000000000002 -- bittorrent
        19d4aafe-0d6d-4bb8-913d-6f0541a6ee11 -- Alpha [origin]
        6da720cc-4583-429d-bde0-724b7f9e494a -- Delta [here]
        8523418a-0c1b-4987-a048-c967fc5ec1e7 -- Beta
untrusted repositories: 0
transfers in progress: none
available local disk space: 123.11 gigabytes (+1 megabyte reserved)
local annex keys: 0
local annex size: 0 bytes
annexed files in working tree: 2
size of annexed files in working tree: 2.59 megabytes
bloom filter size: 32 mebibytes (0% full)
backend usage: 
        SHA256E: 2
```

What is wrong there? My mental model or some git-annex issue?

Thanks,
Florian
