Add support for the lines attribute

README.adoc

@@ -35,6 +35,7 @@ Then, inside your AsciiDoc file, use an `include` statement like normal, pointin
 
 * `repository` - path to the Git repository (default: `.`)
 * `revision` - repository revision to use (default: `HEAD`)
+* `lines` - specify the lines to include (i.e. `lines=2..5;10;12`)
 
 // tag::examples[]
 
@@ -74,4 +75,10 @@ Paths within the repository work as usual:
 \include::git@path/within/repo/file.rb[]
 ----
 
+=== Specifying lines to include
+
+----
+\include::git@README.adoc[lines=2..5;10;12]
+----
+
 // end::examples[]

lib/asciidoctor-git-include.rb

@@ -13,13 +13,37 @@ def process doc, reader, target, attributes
     target.slice! "git@"
     repository = attributes.fetch('repository', '.')
     revision = attributes.fetch('revision', 'HEAD')
+    lines = attributes.fetch('lines', '')
 
     cmd = %(git -C #{repository} show #{revision}:#{target})
     content = %x(#{cmd})
 
+    content = process_line_selection(content, lines) unless lines == ""
+
     reader.push_include content, target, target, 1, attributes
     reader
   end
+
+  # inspired by https://github.com/tkfu/asciidoctor-github-include/blob/410e0079b2300596ca2b16c94c23c63459e6d0f8/lib/asciidoctor-github-include.rb#LL79C7-L79C29
+  def process_line_selection content, lines
+    snipped_content = []
+    selected_lines = []
+    text = content.split(/\n/)
+
+    lines.split(/[,;]/).each do |linedef|
+      if linedef.include?('..')
+        from, to = linedef.split('..', 2).map {|it| it.to_i }
+        to = text.length if to == -1
+        selected_lines.concat ::Range.new(from, to).to_a
+      else
+        selected_lines << linedef.to_i
+      end
+    end
+    selected_lines.sort.uniq.each do |i|
+      snipped_content << text[i-1]
+    end
+    snipped_content
+  end
 end
 
 Asciidoctor::Extensions.register do

test/extension_test.rb

@@ -35,6 +35,21 @@ class ExtensionTest < Minitest::Test
 
       assert_match(/Other repo\./, output)
     end
+
+    test 'it includes selected lines from a file in the git repository' do
+      input = <<-EOS
+include::git@test/fixtures/multiline.adoc[lines=2..3;5]
+      EOS
+
+      output = render_embedded_string input
+
+      refute_match(/Line 1\./, output)
+      assert_match(/Line 2\./, output)
+      assert_match(/Line 3\./, output)
+      refute_match(/Line 4\./, output)
+      assert_match(/Line 5\./, output)
+      refute_match(/Line 6\./, output)
+    end
   end
 
   def given_file_committed_to_fresh_repo(file_name)