How to delete all merged branches in GIT?

Question

I tend to accumulate lots of branches as I'd do one branch per feature. When cleaning up, I'd like to
delete all branches, which have been merged.

I could use

 $ git branch -d (which was merged already?) ^C
 $ git branch --merged # let's find out
 ...
 $ # Now run git branch -d with each of the branches.

This kind of question has already been discussed,
http://stackoverflow.com/questions/6127328/how-can-i-delete-all-git-branches-which-are-already-merged
suggests: git branch --merged | grep -v "*" | xargs -n 1 git branch -d

I could think of:

 $ git branch -d --merged # no need to specifiy a branch iff --merged is given with -d
 $ git branch --delete-merged # comes as an new extra option, doesn't clutter other commands
 $ git branch -d keyword-for-all-merged-branches

Before starting such a feature, I'd like to hear input of others.

Answer 1

Maybe someting like:
- check you're on master
- only consider branches that begin with first-last-/

head=$(git rev-parse --verify HEAD)
master=$(git rev-parse --verify master)

if test "$head" != "$master"; then
 echo "You must be on master"
 exit 1
fi

git branch --merged |
sed -n -e 's/ *//' -e '/^[^/][^/]//p' |
xargs git branch -d