git_housekeeping.zsh

#!/bin/zsh

# Fetch changes from the remote repository and prune (delete) remote tracking branches that no longer exist on the remote
git fetch --prune && \
# Display a list of local branches and their associated remote branches
git branch -vv | \
# Extract lines related to deleted remote branches
grep ': gone]' | \
# Extract branch names from the lines that were extracted
awk '{print $1}' | \
# Receive branch names and delete the corresponding local branches; the -r option prevents the command from running if there are no arguments
xargs -r git branch -d

one-liner

git fetch --prune && git branch -vv | grep ': gone]' | awk '{print $1}' | xargs -r git branch -d