This essential feature doesn’t exist, I bought both Sublime and Merge (150$) and still have to resolve conflicts with the files with other software or manually.
The files look sometimes like this
>>>>> HEAD ....
..
..
=================
...
=================
Sublime Merge provides a 3-way-diff to resolve conflicts.
If you however just hit “stage” on those files or “stage all” the content is saved/staged as is, including bare conflict markers.
You may probably look for bluish diff headers with a “Resolve” button on the right.
Hitting “Resolve” button opens the diff
I spent weeks bemoaning the lack of this feaiure before spotting that button. No idea how I missed it - same blindspot as the OP 
