I have two branches that have diverged. I need to merge *most* of /master into the new branch but not all of it. I tried "Merge master into current branch" but it, of course, overwrote files I didn't want it to. I'm hoping to find some sort of "manual-but-not-manual merge" where it would prompt me for each change and I could step through and select which ones to merge.
I can do this in WinMerge (and have been) but it takes a LONG time to generate the diff.
Does SourceTree have anything like this?
It depends if your file changes are cleanly encapsulated by atomic single file commits.
If they are then you could use either cherry-picking, if you want history, or patch files, if history doesn't matter. Either of which can be done in Sourcetree.
If they aren't then I think you are in to the world of rebasing. The following gives some pointers https://stackoverflow.com/a/449632. Sourcetree can help with this, but you may well find it easier to follow the examples using the command line.
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