Change `git init`s default behavior to use `main` branch.

git-init-to-main

#!/bin/sh -eu

echo '=== Changing `git init` to default to "main" branch.'
echo "+ Updating ~/.gitconfig"
cat <<'EOF' >> ~/.gitconfig
[init]
    templateDir = ~/.config/git/template/
EOF

ROOT_TEMPLATE_DIR=""
if [ "$(uname)" = "Darwin" ]; then
  ROOT_TEMPLATE_DIR=/Library/Developer/CommandLineTools/usr/share/git-core/templates/
elif [ "$(uname)" = "Linux" ]; then
  ROOT_TEMPLATE_DIR=/usr/share/git-core/templates
fi
if [ -z "$ROOT_TEMPLATE_DIR" ]; then
  echo "No root template directory. Stopping."
  exit 1
fi
cp -r "$ROOT_TEMPLATE_DIR" ~/.config/git/template

echo "+ Updating ~/.config/git/template/HEAD"
cat <<'EOF' > ~/.config/git/template/HEAD
ref: refs/heads/main
EOF