Right, no Linux desktop client at the moment. I don't think it would be especially difficult to make one, but we'd need enough demand to make the investment.
But having said that, we do provide WebDAV API. Every modern OS I know of, including Linux, can mount a file system over WebDAV. It is not very efficient, and doesn't have all the features you would get with a client, but at least you have access to your files.
Some people actually prefer to use only WebDAV, because that way as soon as you cut network connectivity the files are not accessible (security feature).
Ok, so you haven't automated merge conflict resolution.
There are also cryptographically signed documents which you cannot merge, because that would break signatures.
So the question is, how much automated merge processing should be done, and how big are the risks in doing so. Even if the system were capable of doing merges for some documents, it would need to have a setting to turn it off. Recovering erroneously merged documents also needs some thinking. And so forth.
So bottom line is I guess we agree that in some cases merges can be done, automated to some level even, but there is a lot of work needed to make it safe, understandable and usable for the majority of users.
Can you explain how you merge two PDF documents that started as a single document, and was edited by two people at the same time? What do you do when they edited the same part of the document? And what about Word, JPEG, MOV etc.?
In source control systems like Subversion the application can usually automatically merge changes that happen in different parts of the document, but will require user intervention to merge conflicts. Merge conflicts can be difficult to resolve even in plain text. I really don't know how you could automate that in plain text files, let alone arbitrary file formats.
I know at least Egnyte (https://www.egnyte.com/) offers folder permissions, and has clients on Windows, Mac, Android, iPhone and iPad. The Linux client is available on some NAS devices and also as a VMWare appliance.
But having said that, we do provide WebDAV API. Every modern OS I know of, including Linux, can mount a file system over WebDAV. It is not very efficient, and doesn't have all the features you would get with a client, but at least you have access to your files.
Some people actually prefer to use only WebDAV, because that way as soon as you cut network connectivity the files are not accessible (security feature).