On a team where Git is the source control mechanism, I do expect every developer to know how to use Git. And to a designer on that team, Git will be central to

On a team where Git is the source control mechanism, I do expect every developer to know how to use Git. And to a designer on that team, Git will be central to their workflow, assuming their workflow requires editing the site design. If a developer needed to edit images regularly, I would expect them to learn enough Photoshop to do it, not to go bother a designer every time because Photoshop isn't a "developer tool". For someone who can understand Photoshop layers, understanding commit, push, and pull shouldn't take too long!