Delete local branches that have been merged into master (except master itself, with optional -f)

git-trim

#!/usr/bin/env bash

BRANCH="main"

if [ $# -eq 1 ] ; then
  BRANCH=$1
fi

MERGED_BRANCHES=$(git branch --merged $BRANCH | grep -v '^[ *]* '"$BRANCH"'$')

if [ -z "$MERGED_BRANCHES" ]; then
  exit 0
fi

echo "$MERGED_BRANCHES" | xargs git branch -d
 
# git trim    :: list all branches that are merged into a specified branch (default: main),
#                filtering out the target branch itself, and then delete only those branches
#                that are fully merged (safe, deletes local branches only)

Updated to use echo and pipe into xargs instead of doing git branch --merged and piping into grep again (was repeating myself)