Show the latest activity on each branch

The following command shows a list of all branch heads (including their last activity dates):

$ git log --simplify-by-decoration --decorate \
          --date=relative --date-order \
          $(git branch -a | cut -c 3- | grep -v -- '->')

Branches near the bottom haven't been touched recently.

I'd recommend creating an alias for it:

$ git config --global alias.activity '!git log --simplify-by-decoration --decorate --date=relative --date-order $(git branch -a | cut -c 3- | grep -v -- "->")'