Another tool worth mentioning is Sublime Merge, the standalone git UI from the Sublime Text team. It’s hands-down the best commit, history, tree, and branch browsing and management tool I’ve found so far, and as the name implies it has an excellent conflict resolution mode for performing merges. It’s what I usually reach for the moment a git operation starts looking more complex than the simple git add, git commit cycle. (I still do those from the command line, because I’m old.)
Sublime Merge is useful even if (or maybe especially if) you’re not a Sublime Text user. I prefer to edit code with Atom, which is “fine” for creating new commits. But Atom’s history-exploration features leave something to be desired, and its merge features are little more than a slightly-prettier, colorful version of the in-file <<<<<< / ======/ >>>>>>> markup. Sublime Merge uses a three-pane, side-by-side view that makes merges clearer, since you can always see the entirety of both “before” states, as well as the final outcome of the merge in the middle pane.
(Edit: Another point in its favor: Sublime Merge is also available for Linux.)
