Functions to remove branchs that was merged but not deleted

del_branch.fish

#
# filepath ~/.config/fish/functions/del_branch.fish
#

function del_branch --argument name
    for name in $argv
        # Check if the branch exists locally
        set -l local_exists (git rev-parse --verify --quiet $name)

        # Check if the branch exists remotely
        set -l remote_exists (git ls-remote --heads origin $name)

        # If the branch exists locally, delete it
        if test -n "$local_exists"
            git branch -D $name
            # Check if deletion was successful
            if test $status -ne 0
                echo "Failed to delete local branch $name."
            end
        else
            echo "No local branch named $name."
        end

        # If the branch exists remotely, delete it
        if test -n "$remote_exists"
            git push origin --delete $name
            # Check if deletion was successful
            if test $status -ne 0
                echo "Failed to delete remote branch $name."
            end
        else
            echo "No remote branch named $name."
        end
    end
end

del_branch_completions.fish

#
# filepath ~/.config/fish/completions/del_branch.fish
#

function __fish_del_branch_complete
    # Fetch and list both local and remote branch names, removing 'origin/' prefix from remote branch names
    set -l branches (git for-each-ref --format '%(refname:short)' refs/heads refs/remotes | string replace -r '^origin/' '')

    # Remove duplicates by converting to a set
    set -l unique_branches (echo $branches | tr ' ' '\n' | sort -u)

    for branch in $unique_branches
        switch $branch
            case HEAD
                # Skip this entry
            case '*'
                # Output branch names
                echo $branch
        end
    end
end

complete -f -c del_branch -a '(__fish_del_branch_complete)'

git_prune.fish

#
# filepath ~/.config/fish/functions/git_prune.fish
#

git fetch --prune --all
set -l deleted_branches (git branch -vv | grep ": gone]" | awk '{print $1}')
if [ (count $deleted_branches) -eq 0 ]
    echo "No branches to delete"
else
    for branch in $deleted_branches
        git branch -D $branch
    end
end

How to use it:

del_branch works for multiple branchs

$ del_branch <name_of_the_branch> <name_of_the_branch>

git_prune

$ git_prune