Anyone can recommend a solution for this?
As far as I know, Panic has not announced any specific plans to include support for Git in Coda, but it seems unlikely that it won't make it into the app at some point.
For now, there are two Git GUIs for OS X (not including gitk): GitX and Gity. Both have plugins for Coda, but it's not quite the direct integration you might be looking for. Check out the two apps and their respectively plugins here: