$ gem install mdtoc

$ mdtoc --help
Usage: mdtoc [options] files or directories...
    -h, --help                       Show this message
    -o, --output PATH                Update a table of contents in the file at PATH
    -a, --[no-]append                Append to the --output file if a <!-- mdtoc --> tag isn't found
    -c, --[no-]create                Create the --output file if it does not exist

$ echo '<!-- mdtoc -->' >> README.md

$ mdtoc -aco README.md test/samples

task default: %w[mdtoc]

desc 'Update Markdown table of contents and push changes to the git repository'
task :mdtoc do
  command = <<~CMD
    set -e
    if [ -n "$(git diff --name-only --diff-filter=U)" ]; then
      echo 'Error: conflicts exist' >&2
      exit 1
    fi
    mdtoc --append --create --output README.md docs/
    git add *.md **/*.md
    git commit -qm 'Update TOC' || true
    git pull
    git push
  CMD
  sh command, verbose: false do |ok, status|
    unless ok
      fail "Failed with status: #{status.exitstatus}"
    end
  end
end

# Install dependencies
$ bundle

# List rake tasks
$ rake -T
rake build                 # Build mdtoc-0.0.2.gem into the pkg directory
rake default               # Run the build, rubocop:auto_correct, sorbet and test tasks
rake install               # Build and install mdtoc-0.0.2.gem into system gems
rake install:local         # Build and install mdtoc-0.0.2.gem into system gems without...
rake release[remote]       # Create tag v0.0.2 and build and push mdtoc-0.0.2.gem to ru...
rake rubocop               # Run RuboCop
rake rubocop:auto_correct  # Auto-correct RuboCop offenses
rake sorbet                # Run the Sorbet type checker
rake test                  # Run tests

# Run mdtoc with test inputs
$ ruby -Ilib bin/mdtoc test/samples

# Run mdtoc with test inputs, and write to a newly created output file
$ f=$(mktemp) && ruby -Ilib bin/mdtoc -aco ${f} test/samples ; cat ${f}