SourceTree is actually a pretty good GUI for git; it shows the commit tree just like you said.
The visualization features are amazing though but could use a little bit more design.
If you're talking about locally modified files, I use the integration with Visual Studio to manage those and it is doing an OK job. The only gripe I have with it is that you can't change an already staged file or those changes won't get checked in. I don't remember it working like that a year ago so something must have changed.
I use them a lot and love how it makes some advanced stuff much easier (committing hunks, interactive rebases). They're also cross platform, which is great.
Still, it's incredible how crappier it gets over time. It feels like every year there's some kind of new major refactor or UI framework refresh that just destroys whatever little stability the application had, as if a new lead comes in and decides to start everything from scratch.
As an engineer I kinda understand the reasoning (using a nuclear bomb to get rid of tech debt), but it's pretty baffling from a product lifecycle standpoint.
I wish they had a more stable model and were charging for registration really. I'd gladly pay them $50 or whatever for some modicum of stability.
I mostly only ever used it for branches, cherry picking and conflict resolution, and it was awesome for that.
I don't use it now, and I don't use branches or cherry picking. My personal philosophy is that I am not keen on branches: never have been, never will be. I see repositories as a two pizza team concept. If you need branches, you should split the repo, make more iterative changes, or look at establishing or improving a test suite. It keeps things simple and cognitively low overhead for everyone (as per the sqlite team's comments).
I work on a branch, raise a merge request to master, let my colleague do a check and point out any issues and then merge it once we're both happy with it. He does the same thing for me to check.
Other than that, no branches.
It is not immediate, needs to wait for another human to be around and mentally present, demands some sort of QA standards are created and commonly understood, and creates the need to make and manage a forum for listing and discussing merge requests.
You could get some of the way and retain instant feedback with automated tests, yet remove a lot of the overhead.