To see the differences between two branches in a Git reposiory, use:
$ git diff branch_1 branch_2
If you already have a
difftool setup (something like Kaleidoscope), you can view the DIFFs using:
$ git difftool branch_1 branch_2
Both commands will produce the diff between the tips of the two branches. The same syntax works for comparing a branch with a tag or a tag with another tag. Note that you can also add a file or folder name after the above two commands.