I'm not sure why you miss the merge thing, because I never used it myself (I used for request, but not for merge).

Let's use my case (Spanish translation of Pumpa).
I update my local clone with upstream changes, then I push it to my public clone. Then, I make a branch “Spanish”, then I commit my changes, push my branch to my public clone, send you the URL of the branch via issue tracker (instead of requesting merge, I open an issue and comment on there). For my side is ok, only slight changes.

Then you update your local repo adding my branch as remote, and compare, and merge (or not). I suppose you were merging via the web interface, and noe, you need to use a desktop client. Aren't there good desktop viewers (git clients) for that task? Or am I missing something?