Allow using backticks to quote text in RDoc markup too

doc/markup_reference/rdoc.rdoc

@@ -756,17 +756,32 @@ Rendered HTML:
   <tt>Monofont passage containing _italics_ and *bold*.</tt>
 
 A single word may be made monofont by a shorthand:
-prefixed and suffixed plus-signs.
+prefixed and suffixed plus-signs or backticks.
 
 Example input:
 
   +Monofont+ in a paragraph.
 
+  `Monofont` in a paragraph.
+
 Rendered HTML:
 
 >>>
   +Monofont+ in a paragraph.
 
+  `Monofont` in a paragraph.
+
+Note: The shorthand (<tt>+...+</tt> and <tt>`...`</tt>) only works for simple content
+containing word characters, colons, periods, slashes, brackets, and hyphens.
+Content containing HTML tags or other markup delimiters will not be matched.
+For complex content, use the HTML tags <tt><tt></tt> or <tt><code></tt> instead:
+
+  <tt>+literal_plus+</tt> shows: +literal_plus+
+
+  <tt>`literal_backtick`</tt> shows: `literal_backtick`
+
+  <tt><code>content</code></tt> shows: <code>content</code>
+
 ==== Strikethrough
 
 Text may be marked as strikethrough via HTML tag <tt><del></tt> or <tt><s></tt>.

lib/rdoc/markup/attribute_manager.rb

@@ -89,6 +89,7 @@ def initialize
     add_word_pair "*", "*", :BOLD, true
     add_word_pair "_", "_", :EM, true
     add_word_pair "+", "+", :TT, true
+    add_word_pair "`", "`", :TT, true
 
     add_html "em", :EM, true
     add_html "i",  :EM, true
@@ -100,7 +101,7 @@ def initialize
 
     @word_pair_chars = @matching_word_pairs.keys.join
 
-    # Matches a word pair delimiter (*, _, +) that is NOT already protected.
+    # Matches a word pair delimiter (*, _, +, `) that is NOT already protected.
     # Used by #protect_code_markup to escape delimiters inside <code>/<tt> tags.
     @unprotected_word_pair_regexp = /([#{@word_pair_chars}])(?!#{PROTECT_ATTR})/
   end

test/rdoc/markup/attribute_manager_test.rb

@@ -244,6 +244,31 @@ def test_convert_attrs_ignores_tt_inside_tt
     assert_equal 'foo <CODE>+tt+</CODE> bar', output('foo <tt>+tt+</tt> bar')
   end
 
+  def test_backtick_basic
+    assert_equal(["cat ", @tt_on, "and", @tt_off, " dog"],
+                  @am.flow("cat `and` dog"))
+
+    assert_equal(["cat ", @tt_on, "X::Y", @tt_off, " dog"],
+                  @am.flow("cat `X::Y` dog"))
+  end
+
+  def test_backtick_output
+    assert_equal 'cat <CODE>and</CODE> dog', output('cat `and` dog')
+    assert_equal 'cat <CODE>X::Y</CODE> dog', output('cat `X::Y` dog')
+  end
+
+  def test_convert_attrs_ignores_backtick_inside_code
+    assert_equal 'foo <CODE>`text`</CODE> bar', output('foo <code>`text`</code> bar')
+  end
+
+  def test_convert_attrs_ignores_backtick_inside_tt
+    assert_equal 'foo <CODE>`text`</CODE> bar', output('foo <tt>`text`</tt> bar')
+  end
+
+  def test_backtick_escaped
+    assert_equal ['`text`'], @am.flow('\`text`')
+  end
+
   def test_convert_attrs_ignores_del_inside_code
     assert_equal 'foo <CODE><del>strike</del></CODE> bar', output('foo <code><del>strike</del></code> bar')
   end
@@ -367,7 +392,7 @@ def test_initial_html
   def test_initial_word_pairs
     word_pairs = @am.matching_word_pairs
     assert word_pairs.is_a?(Hash)
-    assert_equal(3, word_pairs.size)
+    assert_equal(4, word_pairs.size)
   end
 
   def test_mask_protected_sequence