setup a good gitconfig

vi ~/.gitconfig

#!/.giconfig
[user]
        name = <username>
        email = <mailaddres>
[init]
        defaultBranch = main
[alias]
    cleanup = "!git branch --merged | grep  -v '\\*\\|master\\|develop\\main' | xargs -n 1 -r git branch -d"

To avoid having thousend of local branches not alligned with the remote repository, just do:

git cleanup