a .del and an adjacent <ins> can still be a diff pair

this makes the common case of "(a)" being turned into a link
"<ref>(a)</ref>" work better as a diff pair

indigo/analysis/differ.py

@@ -209,7 +209,7 @@ def repl(match):
                 return '\xA0' * (b - a)
             del_.text = ws_re.sub(repl, del_.text)
 
-            if ins is None or ins.tag != 'ins' or del_.tail:
+            if del_.tail or ins is None or (ins.tag != 'ins' and not (ins.get('class') or '').startswith('ins ')):
                 ins = del_.makeelement('ins')
                 # non-breaking space
                 ins.text = '\xA0'

indigo/tests/test_differ.py

@@ -71,7 +71,7 @@ def test_inline_tag_added(self):
         )
 
         self.assertEqual(
-            '<p>Some text <span class="diff-pair"><del>bold text and a tail.</del><ins>&#xA0;</ins></span><b class="ins ">bold text</b><ins> and a tail.</ins></p>',
+            '<p>Some text <span class="diff-pair"><del>bold text and a tail.</del><b class="ins ">bold text</b></span><ins> and a tail.</ins></p>',
             diff,
         )