[Sharing] Avoid loop shares

[dragotin]

Consider this szenario:

User Tom shares a directory with the two users Betty and John. 
Now these both decide to share this folder with Carl. So the 
same shared folder would appear twice on Carls data set. 

That must not happen. The server has to check if the shared folder is already there at Carl.

[DeepDiver1975]

@dragotin with respect to syncing is that a critical scenario which needs to be fixed in oc6? Or can this one wait until oc7? THX

[dragotin]

I think it is ok to handle that with oC7.

[nickvergessen]

@schiesbn We talked about circular sharing last week? Is this going to be resolved with that?

[PVince81]

I think at the moment in OC 7 the folder would appear twice with different names, which I believe is acceptable for now.

In OC 8 we'll look into removing reshare chains and make it a single participant list, as stated here #9058 so this issue might be obsolete at that point.

[PVince81]

Just observed a similar case today on master:

1. user1 shares "test" with user2
2. user2 shares "test" with user3
3. user3 shares "test" with user1

Now user1 has two folders "test" and "test (2)" with the same contents.
If you move then rename "test (2)" you can use it almost like a symlink/hardlink 😉

[PVince81]

There was a discussion to change how reshare works: #9058
Basically have a single list of people who have access to the folder instead of having a reshare chain.

[PVince81]

I suggest to defer this to after #9058 is implemented (possibly 8.2)

[MorrisJobke]

#9058 was moved to 9.0 -> move this too.

[DeepDiver1975]

reshares will die in 9.0 -> closing. THX @dragotin