sehe’s solution looks great, here is another one that seems to contain similar information, formatted differently, it uses git log, so it contains commit information as well (ignore the branch names, I kind of messed them up!):
git log --all --graph --decorate --oneline --simplify-by-decoration
* ae038ad (HEAD, branch2-1) add content to tmp1
| * f5a0029 (branch2-1-1) Add another
|/
* 3e56666 (branch1) Second wave of commits
| * 6c9af2a (branch1-2) add thing
|/
* bfcf30a (master) commit 1