Interesting. We solved the problem of file management and versioning by having the designers use Github Desktop. Tracking files, changes, versions, commit messages, etc. is a solved problem.
That said, Figma promises to be the combination of Abstract + Sketch + Invision and thats what has me intrigued. Going to a Figma webinar may ease a lot of my worry.
If you don't mind me asking, how do your designers handle rebasing and conflict resolution?
In a merge, select the desired version (eg `git checkout --theirs -- logo.png` for the version from the branch you're merging into the current branch or `git checkout --ours -- logo.png` for the version from the current branch), then add the file and complete a normal merge commit.
git merge foo
git checkout --theirs -- logo.png
git add logo.png
git commit -m "Merging foo into master"