Convert indented text lists to Markdown outlines

tabs2md.rb

#!/usr/bin/env ruby
# tabs2md
# Brett Terpstra 2012
#
# Convert indented text to Markdown
#
# Great for apps that can copy out indented outlines but not OPML
# For basic outlines (mind maps) to Markdown, faster than OPML
#
# Indents can be tabs or 4 spaces
# no indent = h1
# 1 indent = h2, 2 indents = h3, then nested list items
# Beyond six indents become paragraphs nested in the preceding list item

unless ARGV[0].nil?
	input = File.new(ARGV[0],'r').read
else
	input = STDIN.read
end

input.split("\n").each { |line|
	next if line =~ /^\s*$/
	line.gsub!(/ {4}/,"\t") if line =~ / {4,}\w/
	matches = line.scan(/\t/).length
	case matches
	when 0
		prefix = "\n# "
		addnewline = true
	when 1
		prefix = "\n## "
		addnewline = true
	when 2
		prefix = "\n### "
		addnewline = true
	when 3
		prefix = "* "
	when 4
		prefix = "	* "
	when 5
		prefix = "		* "
	when 6
		prefix = "			* "
	else
		prefix = "\n				"
		addnewline = true
	end
	# suffix = addnewline ? "\n\n" : "\n"
	puts prefix + line.strip
	puts if addnewline
	addnewline = false
}