If I may revive this one, I’d like to add that full support of this feature isn’t necessary for it to be useful. One thing I discovered is that while I’m working on some file in my synced directory (in my case, it’s a LaTex source file for a paper I’m working on, but that shouldn’t restrict the use-case), I tend to make many little amendments in the course of a few hours.
It would be terrific if I could right-click the file and ask Insync to let Google Drive know I want the current version of the file to be kept forever (or, at least, until I’m sure I like the changes I’ve made), because I tend to blow through the 100-versions-Drive-limit and lose valuable previous versions. Any restoration I need to make would be much much rarer, so I can certainly make-do with logging into Drive to do that manually.
Even better, if it would happen automatically for files I haven’t changed in, say, 12-24 hours, and now make 30 new versions in the course of a few hours. Whenever that happens, I’d love for Insync to automatically tag the version I had when the morning started as keep-forever. Let me know if I ever reach the 200-kept-versions limit, or just cycle old versions when we get there; I’m pretty sure that after 200 days working on it, most files will already reach their completed version.