git prune-branches

git-prune-branches.sh

#!/bin/sh

#
# git-prune-branches - prune merged branches
#
# Configurations:
#   .git/protected-branches - one-line regex matching the names of the branches to be protected.
#

if [ "`git branch | grep '^\*'`" != "* master" ]; then
    echo "Error: not on master."
    exit 1
fi

protected_branches=$( cat "`git rev-parse --git-dir`/protected-branches" 2> /dev/null | head -n1 )
protected_branches="${protected_branches}${protected_branches:+|}^master$"

echo "Deleting branches ignoring $protected_branches"

git branch --merged | cut -c3- | egrep -v "$protected_branches" | xargs git branch -d

git remote prune origin

Usage:

$ echo '^dont-delete$|^important-branches/' > .git/protected-branches
$ git checkout master
$ git prune-branches
Deleting branches ignoring ^dont-delete$|^important-branches/|^master$
Deleted branch foo (was fa8a3dd).
Pruning origin
URL: git@github.com:my/repo.git
 * [pruned] origin/foo