Keep plugin's up-to-date via ifttt or subversion on DropBox

Hi there,
I’m unsure where to post this question – I’ve googled it but haven’t found anything really relevant.
What I’d like to do is have a folder on DropBox that contains all the plugin’s I use on client sites (that parts easy) but I’d like the plugins in that folder to be the latest version (ie, I don’t want to have to update them after FTP’ing to my latest site build) I’d rather have them already up-to-date.
So, I was thinking there must be some way to automate that, perhaps using something like ifttt or via subversion (or something).
You know what I’m getting at aye?
Any ideas?
Thanks in advance,
Jas